Several weeks after Donald Trump secured the Republican presidential nomination, his national campaign co-chairman urged a foreign policy adviser to meet with Russian officials to foster ties with that country's government.

"Make the trip, if it is feasible," Sam Clovis wrote in an August email to George Papadopoulos.

The email, included in court papers unsealed Monday, shows how an otherwise low-profile adviser has become a focus of the federal probe into possible coordination between the Trump campaign and the Kremlin.

Papadopoulos was in contact with several senior Trump campaign aides about his efforts to broker a relationship between Trump and Russian President Vladimir Putin, the court papers show. In addition to Clovis, who now serves as senior White House adviser to the U.S. Department of Agriculture, Papadopoulos wrote to campaign manager Corey Lewandowski and campaign chairman Paul Manafort, the newly released documents show.

The campaign officials are not identified in court documents, but some of the emails cited by federal prosecutors match messages described in August to The Washington Post by people familiar with their contents.

The newly released documents show that while senior Trump officials at times rebuffed or ignored Papadopoulos, they were well aware of his efforts, which went on for months. His interactions with them could complicate the White House's attempts to distance the president from Papadopoulos, who pleaded guilty Oct. 5 to lying to federal agents.

[Trump campaign emails show aide’s repeated efforts to set up Russia meetings]

Trump himself knew of Papadopoulos's claims that he had a pipeline to Moscow: During a March 2016 meeting of the campaign's national security advisers in Washington that Trump attended, Papadopoulos said he had connections that could help arrange a meeting between the then-candidate and Putin.

On Monday, White House press secretary Sarah Huckabee Sanders said she was "not sure that the president recalls specific details of the meeting," calling it "brief." She described Papadopoulos's role with the campaign as "extremely limited."

In a statement, Clovis's attorney Victoria Toensing said Clovis, a radio host from Iowa who was one of Trump's earliest supporters, "always vigorously opposed any Russian trip for Donald Trump and/or the campaign."

She said Clovis was "being polite" when he encouraged Papadopoulos to meet with Russian officials in August, adding that the campaign had a "strict rule that no person could travel abroad as a representative of the campaign." Clovis could not stop an American citizen from traveling abroad "in his personal capacity," she said.

Clovis has been nominated to be the top science adviser at the USDA. His hearing before the Senate Agriculture Committee is scheduled for Nov. 9.

Lewandowski did not respond to a request for comment.

In a statement, Papadopoulos's attorneys Thomas Breen and Robert Stanley said they would refrain from commenting on the case.

"We will have the opportunity to comment on George's involvement when called upon by the Court at a later date," they said. "We look forward to telling all of the details of George's story at that time."

Trump first identified Papadopoulos as one of his advisers in a March 2016 meeting with The Post's editorial board, describing him as "an energy and oil consultant. Excellent guy."

[‘Anyone . . . with a pulse’: How a Russia-friendly adviser found his way into the Trump campaign]

Papadopoulos was charged under seal in July and was arrested when he arrived at Dulles International Airport on July 27. His plea agreement indicates that he is cooperating with special counsel Robert S. Mueller III. He pleaded guilty in October to lying to federal agents about his contacts with people with connections to the Russian government, filings show.

Papadopoulos's efforts to arrange a meeting with Russian officials began days after he was named to Trump's campaign team and continued for months. At one point, he emailed Lewandowski "to discuss Russia's interest in hosting Mr. Trump. Have been receiving a lot of calls over the last month about Putin wanting to host him and the team when the time is right," according to documents.

A month later, he reiterated Russia's interest in an email to Manafort.

In response, Manafort forwarded Papadopoulos's offer to his deputy Rick Gates, writing, "We need someone to communicate that [Trump] is not doing these trips. It should be someone low level in the campaign so as not to send any signal."

Manafort spokesman Jason Maloni told The Post in August that the campaign chairman's response indicated that "any invitation by Russia, directly or indirectly, would be rejected outright."

Papadopoulos's proposed trip ultimately did not take place, court documents show.

[Paul Manafort, Rick Gates charged by special counsel]

According to court papers, Papadopoulos lied to federal agents about one of his key contacts: a London-based professor he met in Italy in March 2016, days after he joined the Trump campaign.

In a subsequent meeting in April, the professor told Papadopoulos that the Russian government had "dirt" on Democratic presidential candidate Hillary Clinton, including thousands of Clinton's emails.

That conversation occurred weeks before the Democratic National Committee revealed that it had been hacked and believed that Russians were behind the attack. It also came about a month after an email account belonging to Clinton's campaign chairman, John Podesta, was targeted with a phishing attempt that may have led to the hack of his emails. Podesta's emails were released by WikiLeaks in October 2016.

One email quoted in court filings regarding the professor matches an exchange previously described to The Post in which Papadopoulos identified the professor as Joseph Mifsud, the director of the London Academy of Diplomacy.

That document, as well as emails with Clovis and other top campaign aides, was among more than 20,000 pages that the Trump campaign turned over to congressional committees after review by White House and defense lawyers.

Mifsud told The Post in an email in August that he had "absolutely no contact with the Russian government" and said his only ties to Russia were through academic links. He did not respond to a request for comment Monday.

When asked about the unsealed indictments Monday, Kremlin spokesman Dmitry Peskov said, "We don't know what the charges are." After being sent a copy of the indictments, he responded, "My office hours are over!"

Papadopoulos also communicated with a Russian woman with ties to the government and a man in Moscow he believed was connected to the Ministry of Foreign Affairs, filings show.

At the time, Papadopoulos incorrectly believed that the Russian woman was a niece of Putin, according to court documents.

"We are all very excited by the possibility of a good relationship with Mr. Trump," she wrote to him in April 2016. "The Russian Federation would love to welcome him once his candidature would be officially announced."

[Timeline: How Papadopoulos tried to work with the Russian government]

According to court filings, she told Papadopoulos that she would like to help set up meetings with her associates to discuss U.S.-Russia ties under a future President Trump.

After Papadopoulos emailed campaign officials about her offer, Clovis responded that he would "work it through the campaign," but added, "Great work."

Toensing described Clovis as a "polite gentleman from Iowa" who "would always have been courteous to a person offering to help the campaign."

Clovis played a key role in boosting Trump during the Iowa caucuses, but his influence within the campaign subsequently waned amid tense relations with Trump's son-in-law and adviser Jared Kushner.

During a Jan. 27, 2017, interview with FBI agents, Papadopoulos said he had met the Russian woman before he joined the Trump campaign and falsely stated that he had no relationship with her, according to court filings.

The day after his second interview with FBI agents, in February, Papadopoulos deactivated his Facebook account, which had information about his outreach to Russian officials — a move prosecutors said was aimed at obstructing their investigation.

Papadopoulos, who has a scant foreign policy background, briefly advised the 2016 presidential campaign of neurosurgeon Ben Carson.

When Trump identified Papadopoulos as an adviser in March 2016, the hotel and real estate executive was rising in the field of Republican presidential candidates, and his campaign was eager to show that it had credible voices offering advice on foreign policy. Among the other advisers he named that day was Carter Page, another energy consultant whose ties to Russia have been under scrutiny.

Throughout the summer, Papadopoulos met with foreign officials and gave interviews to media in other countries, sometimes describing Trump's views on Putin or Russia.

He told a group of researchers in Israel that Trump saw Putin as "a responsible actor and potential partner," according to a column in the Jerusalem Post; later he met with a British Foreign Office representative in London and a Greek official in New York, British and Greek embassy spokesmen have said. He also criticized U.S. sanctions on Russia in an interview with the Russian news outlet Interfax.

The Post has also reported that Sergei Millian, who was a key source of information contained in a dossier about Trump's ties to Russia, told people around him that he was in contact with Papadopoulos during the campaign.

Robert Costa, Carol D. Leonnig and Philip Rucker in Washington, Karla Adam in London, and David Filipov in Moscow contributed to this report.