London (CNN) With a backdrop of US war graves, President Donald Trump plunged back into partisan politics with a blazing attack on House Speaker Nancy Pelosi , turning the page on one of the most successful and even-tempered foreign trips of his presidency.

Trump, speaking from the Normandy American Cemetery, blasted the Pelosi as a "disgrace" after Politico reported that she said, "I don't want to see him impeached, I want to see him in prison."

His broadside underscored his code of striking back hard when he is criticized, whatever the circumstances, as well as the increasingly vitriolic relationship between the two leaders at a time when Democrats are accelerating investigations against the President.

"I've tried to be nice to her because I would've liked to have gotten some deals done," he said in the interview from France with Fox News, which aired Thursday night, in response to Pelosi's reported comment. "She's incapable of doing deals."

"She's a nasty, vindictive, horrible person," the President added.

Trump supporters might argue that Pelosi's reported comments -- made behind closed doors -- still break the unspoken "water's edge" tradition of refraining from attacking a President when he is abroad. Trump, though, has often broken the taboo himself -- for instance using a trip to Japan last month to slam Democrats and potential 2020 rival Joe Biden.

When he lands in Washington, the President, who spent the night at his Irish golf resort, will be immediately confronted with a new trade war with Mexico on which he doubled down during his trip to Britain, France and Ireland and is defying mediation efforts.

New confrontations also loom next week, with Democratic leaders who are under rising pressure from rank-and-file lawmakers for impeachment proceedings in response to what they see as Trump's abuses of power in the 2016 election and as President.

Each active front in the perpetual Trump-era political drama in Washington can all or in part be chalked up to his confrontational approach. But at least Trump can reflect, as he flies across the Atlantic, on a five-day journey in which he was both feted by a queen and performed a solemn thank you and farewell to the greatest generation

He reveled in his welcome from Queen Elizabeth II's royal court, was magnanimous toward outgoing British Prime Minister Theresa May and delivered a moving tribute to D-Day veterans in Normandy. The President mostly kept his Twitter salvos targeting his enemies and political jabs for after hours.

British officials were relieved that Trump left the country without any political disasters. The White House, which hasn't had many overseas wins, is also pleased with the trip.

Trump's reception was a reminder of the power of the United States and the institution of the presidency, notwithstanding his poor approval ratings in Europe and the headaches he has caused for allied leaders over the past two years.

The low expectations for Trump's trip, however -- following his outbursts at summits and other unpredictable behavior -- also reflect diminished expectations for this particular White House.

Had any other US President engineered such an overt intervention in domestic UK politics with his comments on the Conservative Party leadership race and Brexit, or seemed so hazy on the details of a possible US-UK trade deal and Northern Ireland, the reaction would have been far more critical.

Mexico showdown

While Trump was in France on Thursday, his team back in Washington was frantically trying to find an off-ramp for the latest tariff confrontation with Mexico, though time to seal a deal is running short.

While the President has sent conflicting signs about his threat to impose 5% tariffs that would escalate by 5% a month if Mexico does not do more to halt the flow of migrants, his vice president and press secretary indicated Thursday that plans for the tariffs were proceeding.

"Something pretty dramatic could happen," Trump told reporters in Ireland on Thursday.

But, he added, "we've told Mexico the tariffs go on. And we mean it, too."

White House press secretary Sarah Sanders said in a statement Thursday afternoon that the US "position has not changed, and we are still moving forward with tariffs at this time."

Vice President Mike Pence echoed that message shortly afterward.

"The President announced 5% tariffs would be imposed on Monday on all goods coming from Mexico. That's the policy of the United States," he said. "The President said what he means and he means what he says."

Trump faces a Friday deadline to sign an executive order to ensure the tariffs go into effect by Monday's deadline.

Trump's sudden offensive against Mexico represents his latest effort to quell a crisis at the border that his hardline rhetoric and flexing of executive power have failed to solve.

In May, more than 144,000 migrants were encountered or arrested at the frontier -- a roughly 32% increase over April and the highest monthly tally in 13 years, according to US officials.

Photos: In pictures: President Trump in Europe US President Donald Trump, visiting the Normandy American Cemetery in France, participates in a ceremony to commemorate the 75th anniversary of D-Day on Thursday, June 6. Hide Caption 1 of 45 Photos: In pictures: President Trump in Europe Trump and his wife, Melania, visit the graves of troops who died on D-Day. Hide Caption 2 of 45 Photos: In pictures: President Trump in Europe The Trumps are joined by French President Emmanuel Macron and his wife, Brigitte, as they watch a flyover on June 6. Hide Caption 3 of 45 Photos: In pictures: President Trump in Europe A World War II veteran shows Trump a photo of himself with the President. Hide Caption 4 of 45 Photos: In pictures: President Trump in Europe Trump addresses the commemoration ceremony in France. Hide Caption 5 of 45 Photos: In pictures: President Trump in Europe Macron and Trump embrace during the D-Day ceremony. Hide Caption 6 of 45 Photos: In pictures: President Trump in Europe A World War II veteran looks over Trump's shoulder during the commemoration ceremony. Hide Caption 7 of 45 Photos: In pictures: President Trump in Europe At a D-Day event held Wednesday, June 5, in Portsmouth, England, Trump reads a prayer that President Franklin D. Roosevelt gave over the radio on D-Day. Hide Caption 8 of 45 Photos: In pictures: President Trump in Europe Trump heads back after speaking at the event in Portsmouth on June 5. Hide Caption 9 of 45 Photos: In pictures: President Trump in Europe Britain's Queen Elizabeth II and Prince Charles play host to the Trumps at the D-Day event in Portsmouth. British Prime Minister Theresa May is at left. Hide Caption 10 of 45 Photos: In pictures: President Trump in Europe Trump meets with German Chancellor Angela Merkel on the sidelines of the D-Day event in Portsmouth. Hide Caption 11 of 45 Photos: In pictures: President Trump in Europe The Trumps pose for a photo ahead of a dinner at Winfield House in London on Tuesday, June 4. Joining them, from left, are Woody Johnson, the US ambassador to the United Kingdom; Camilla, the Duchess of Cornwall; Prince Charles; and Johnson's wife, Suzanne Ircha. Hide Caption 12 of 45 Photos: In pictures: President Trump in Europe Trump and Prince Charles share a toast at Winfield House. Hide Caption 13 of 45 Photos: In pictures: President Trump in Europe Trump and British Prime Minister Theresa May speak at the dinner on June 4. Hide Caption 14 of 45 Photos: In pictures: President Trump in Europe Melania Trump spends time with Camilla and Suzanne Ircha, the wife of the US ambassador. Hide Caption 15 of 45 Photos: In pictures: President Trump in Europe Brexit Party leader Nigel Farage, center, arrives at Winfield House, where the Trumps are staying during their visit. Hide Caption 16 of 45 Photos: In pictures: President Trump in Europe Trump and May give a joint news conference on June 4. "I think she's done a very good job," Trump said, reversing past critiques of her failure to strike a Brexit deal that both Parliament and the EU can accept. Hide Caption 17 of 45 Photos: In pictures: President Trump in Europe Trump and May are followed by their spouses as they make their way to the news conference in London on June 4. The President offered plenty of praise for May, who recently announced her resignation. Hide Caption 18 of 45 Photos: In pictures: President Trump in Europe Philip May and Melania Trump attend a garden party at No. 10 Downing Street. Hide Caption 19 of 45 Photos: In pictures: President Trump in Europe Larry, the No. 10 Downing Street cat, sits underneath The Beast, the presidential armored Cadillac. Hide Caption 20 of 45 Photos: In pictures: President Trump in Europe Trump speaks opposite May at a business roundtable discussion in London. Hide Caption 21 of 45 Photos: In pictures: President Trump in Europe Trump stands next to Queen Elizabeth II before a state banquet at Buckingham Palace on Monday, June 3. Joining them are Melania Trump, Prince Charles and Camilla. Hide Caption 22 of 45 Photos: In pictures: President Trump in Europe The state banquet had a few hundred guests, including several of Trump's children. Hide Caption 23 of 45 Photos: In pictures: President Trump in Europe Trump and the Queen laugh during the state banquet. Hide Caption 24 of 45 Photos: In pictures: President Trump in Europe The Trumps tour Westminster Abbey on June 3. Hide Caption 25 of 45 Photos: In pictures: President Trump in Europe The President signed the guestbook at Westminster Abbey. "Thank you so much," his message said. "This has been a great honor. Special place." Hide Caption 26 of 45 Photos: In pictures: President Trump in Europe The Trumps are joined by Prince Andrew as they pay their respects at the Tomb of the Unknown Warrior in Westminster Abbey. Hide Caption 27 of 45 Photos: In pictures: President Trump in Europe The President's convoy drives down Pall Mall in London on June 3. Hide Caption 28 of 45 Photos: In pictures: President Trump in Europe Queen Elizabeth II welcomes the Trumps to Buckingham Palace. She took them on a tour of the royal collection. Hide Caption 29 of 45 Photos: In pictures: President Trump in Europe Among the items on display was "American Pewter Thoroughbred," a gift that Trump gave the Queen last year. Hide Caption 30 of 45 Photos: In pictures: President Trump in Europe Trump inspects a guard of honor at Buckingham Palace. Hide Caption 31 of 45 Photos: In pictures: President Trump in Europe The US National Anthem is played during a welcoming ceremony at Buckingham Palace. From left are Melania Trump, the Queen, Trump, Charles and Camilla. Hide Caption 32 of 45 Photos: In pictures: President Trump in Europe British Army troops fire a cannon in London's Green Park to mark the beginning of Trump's visit. Hide Caption 33 of 45 Photos: In pictures: President Trump in Europe The Queen greets the President as he arrives at Buckingham Palace. Hide Caption 34 of 45 Photos: In pictures: President Trump in Europe Prince Charles greets Trump as he steps off Marine One at Buckingham Palace. Hide Caption 35 of 45 Photos: In pictures: President Trump in Europe The Trumps are welcomed in London by Charles and Camilla. Hide Caption 36 of 45 Photos: In pictures: President Trump in Europe Trump's daughter Ivanka, who is also advisor to the President, looks out of a window at Buckingham Palace. Hide Caption 37 of 45 Photos: In pictures: President Trump in Europe People outside Buckingham Palace photograph the Changing of the Guard ahead of Trump's arrival on June 3. Hide Caption 38 of 45 Photos: In pictures: President Trump in Europe The Trumps arrive at Winfield House, the residence of the US ambassador, on June 3. Hide Caption 39 of 45 Photos: In pictures: President Trump in Europe Amnesty International installs "Resist Trump" banners on Vauxhall Bridge in London. Hide Caption 40 of 45 Photos: In pictures: President Trump in Europe Marine One flies past the BT Tower in London. Hide Caption 41 of 45 Photos: In pictures: President Trump in Europe The Trumps walk toward Marine One after arriving at London's Stansted Airport on June 3. Hide Caption 42 of 45 Photos: In pictures: President Trump in Europe The President salutes troops as he and the first lady arrive at Stansted Airport. Hide Caption 43 of 45 Photos: In pictures: President Trump in Europe Trump is greeted by UK Foreign Secretary Jeremy Hunt after arriving at the airport. Hide Caption 44 of 45 Photos: In pictures: President Trump in Europe The Trumps arrive at Stansted Airport. 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Uncertainty over which way the President will lean on Mexico deepened when he tweeted early Thursday that "progress is being made, but not nearly enough!"

His hint of flexibility in Ireland could be a sign that he is feeling heat from Republican senators, who have not ruled out an attempt to block the tariffs from going into force.

If the President's hard-line tactics force Mexico to do more to halt the large numbers of undocumented migrants -- or even if it offers cosmetic concessions -- Trump could claim a political victory. But the spat is yet another indication of how his reliance on tariffs as a primary foreign-policy tool maneuvers him into tough political corners.

Talks on the showdown intensified in Washington on Thursday, stretching into the night, and officials from the White House, the State Department and the Department of Homeland Security met to discuss next steps.

"What Mexico is offering is not enough," said Mercedes Schlapp, White House director of strategic communications.

Mexican President Andres Manuel Lopez Obrador said Thursday, however, that he was "optimistic" a deal could be reached.

'I want to see him in prison'

If the President's latest clash with Mexico does get solved before Monday, next week is still certain to see a worsening of Washington's already fractious political climate.

Democrats on Thursday released the text of a contempt resolution targeting Attorney General William Barr and ex-White House counsel Don McGahn ahead of a full House vote next week.

New controversy is surrounding Pelosi, who is facing rising pressure in her Democratic caucus to subject Trump to the drama of an impeachment inquiry.

Politico reported that at a meeting on Tuesday night in which House Judiciary Chairman Jerry Nadler asked to open proceedings against the President, Pelosi said: "I don't want to see him impeached, I want to see him in prison."

The report, quoting multiple Democratic sources, was not denied by Pelosi's office. The speaker has been loath to initiate the impeachment process, fearing that it could backfire and give the President a platform to boost his reelection effort.

The report added extra spice to the already tumultuous relationship between Trump and Pelosi, the two most politically powerful figures in Washington, who are both constantly sculpting the battlefield ahead of the 2020 election.

Republicans, who control the Senate and are unlikely to vote to convict Trump in any impeachment trial, are already capitalizing on the reported remark to hint at Democratic overreach.

"She didn't say that. No, she didn't say that," said Sen. Chuck Grassley, R-Iowa. "To go to prison, you've got to violate a law. What law's been violated?"