WASHINGTON (Reuters) - Leading U.S. lawmakers, including numerous Republicans, criticized President Donald Trump on Monday for failing to confront Russian President Vladimir Putin over Moscow’s meddling in the 2016 U.S. election as the two heads of nuclear powers stood side-by-side at a joint news conference.

U.S. Senate Democratic leader Charles Schumer speaks to the news media about President Donald Trump's summit with Russian President Vladimir Putin at the U.S. Capitol building in Washington, U.S., July 16, 2018. REUTERS/Leah Millis

Trump, speaking in Helsinki after his first summit with Putin, said he saw no reason to believe his own country’s intelligence agencies over the Kremlin leader’s assurances that Russia did not interfere in the U.S. election.

A wave of condemnation immediately followed, with lawmakers calling Republican Trump “weak” and “cowardly,” while Senator John McCain said the summit was “a tragic mistake.” The war hero and former Republican presidential nominee, a frequent critic of the president, said Trump “failed to defend all that makes us who we are - a republic of free people dedicated to the cause of liberty at home and abroad.”

Trump will meet with members of Congress on Tuesday, the White House said without giving further details.

On Friday, a U.S. special counsel unveiled indictments of 12 Russian spies on charges of hacking Democratic Party computers as part of election meddling, the second set of charges against Russians in a probe that Trump calls a political witch hunt.

After the Helsinki summit, at least two senators - Republican Pat Toomey and Senate Democratic Leader Chuck Schumer - raised the possibility of imposing new punishment on Russia.

Toomey said in a statement that unless Putin helps the United States prosecute Russians accused in the hacking, “the United States should impose tough new sanctions on Russia.”

It was unclear if Senate or House of Representatives leaders would back such a move or how new sanctions might be crafted.

Relations between Washington and Moscow have been at their lowest point in the post-Cold War era. Trump touted the summit as a chance to improve ties. Even before the allegations of Russian meddling, tensions were high over Moscow’s concerns about NATO expansion, Russian annexation of the Crimea peninsula from Ukraine in 2014 and Russia’s military backing of Syrian President Bashar al-Assad in its seven-year civil war.

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Trump’s eagerness to improve U.S. relations with Russia had been met with skepticism in Congress, where lawmakers nearly unanimously approved tough sanctions targeting Moscow in 2017.

Former Vice President Joe Biden, a Democrat, weighed in after the summit.

“Flattering dictators will not advance American interests. It makes us less safe,” Biden said of Trump’s remarks.

‘RUSSIAN MEDDLING’

Director of National Intelligence Dan Coats, a Republican and a Trump appointee, responded to Trump’s remarks and stood by the U.S. agencies.

“We have been clear in our assessments of Russian meddling in the 2016 election and their ongoing, pervasive efforts to undermine our democracy,” Coats said.

On his way home, Trump insisted in a post on Twitter that he has “GREAT confidence in MY intelligence people.”

Not all Republicans in Congress were angry with Trump’s conduct in Helsinki. “Absolutely I’m with the president on this; the (U.S.) intelligence community was full of biased people,” Republican Senator Rand Paul told CNN.

House Speaker Paul Ryan, the top Republican in Congress, said Russia undoubtedly interfered in the 2016 election.

“The president must appreciate that Russia is not our ally. There is no moral equivalence between the United States and Russia, which remains hostile to our most basic values and ideals,” said Ryan in a statement.

‘NOT OUR FRIENDS’

Senate Majority Leader Mitch McConnell, a Republican, told reporters: “I’ve said a number of times and I’ll say it again. The Russians are not our friends and I entirely believe the assessment of our intelligence community.”

Senate Foreign Relations Committee Chairman Bob Corker, a Republican, said Trump’s comments next to Putin made the United States look like a “pushover.”

Republican Senator Lindsey Graham said the summit was a “missed opportunity by President Trump to firmly hold Russia accountable for 2016 meddling and deliver a strong warning ...This answer by President Trump will be seen by Russia as a sign of weakness and create far more problems than it solves.”

Senator Susan Collins said Trump’s “position is untenable,” while Senate Intelligence Committee Chairman Richard Burr, also a Republican, outlined Russian aggression on several fronts and said the United States “will not tolerate hostile Russian activities against us or our allies.”

Senate and House Democratic leaders Schumer and Nancy Pelosi went so far as to hint that Trump’s conduct might stem from Putin possibly having embarrassing information about him.

Schumer said Trump’s approach in Helsinki was unprecedented.

“For the president of the United States to side with President Putin against American law enforcement, American defense officials, and American intelligence agencies is thoughtless, dangerous, and weak,” Schumer said.