WASHINGTON — President Trump’s top diplomat faced withering questions from lawmakers Wednesday about the president’s ability to steer US foreign policy and his lack of transparency, as the White House scrambled to present a tougher stance toward Russia.

Secretary of State Mike Pompeo’s appearance before the Senate Foreign Relations Committee came as the White House postponed a second summit with Russian President Vladimir Putin amid criticism of Trump’s conflicting statements on Russian interference in the 2016 presidential election.

In an effort to reassure lawmakers, Pompeo said the president accepts the views of the intelligence community that Russia interfered in the election, and he declared that the United States would never recognize Putin’s annexation of Crimea from Ukraine.

But Tennessee Senator Bob Corker, the top Republican on the panel, told Pompeo that lawmakers are ‘‘filled with serious doubts about this White House and its conduct of American foreign policy.’’

He challenged Pompeo to satisfy bipartisan concerns that the White House is ‘‘making it up as they go’’ and that Pompeo himself may not know what is happening.

Corker complained that senators have been unable to get straight answers to basic questions about what Trump may have said to Putin when the two leaders met in Helsinki last week.

Pompeo testily assured senators that Trump had relayed the contents of the meeting afterward.

Russia and concerns that Trump is too cozy with Putin dominated the three-hour session. The hearing was a symbolic step for Republicans who have frequently set aside long-held policy views about Russia, North Korea, and other issues to suit Trump’s unorthodox approach.

In a sign that the White House wanted to blunt criticism from the president’s own party, the administration issued a declaration about its views on Crimea, including that Republican-approved sanctions will remain in place, hours before the questioning began. White House national security adviser John Bolton then issued a statement postponing the follow-up Putin summit until next year.

Corker’s frustrations followed a week of walk-backs, reversals, and clarifications from a Trump administration trying to account for the president’s freewheeling comments about Russia and the 2016 election.

In recent days, Senate Republicans have made public remarks opposing a future meeting between Trump and Putin, which had been previewed by White House press secretary Sarah Huckabee Sanders last week.

Democrats in Congress, meanwhile, unleashed a torrent of criticism, going so far as calling Trump’s news conference with Putin ‘‘treasonous.’’

On Wednesday, Pompeo said critics were unfairly characterizing Trump administration policy toward Russia as soft, and he ticked off a list of aggressive steps taken, including the expulsion of 60 Russian spies and diplomats, the sanctioning of Russian oligarchs, and the provision of lethal weapons to Ukraine.

When confronted with specific questions about the summit, Pompeo repeatedly recited US policy.

Senator Jeanne Shaheen, Democrat of New Hampshire, asked whether Trump talked to Putin about removing US troops from Syria. Pompeo replied that ‘‘there’s been no change to US policy.’’

‘‘That’s not exactly the question,’’ Shaheen said.

The hearing also provided the first opportunity for lawmakers to ask Pompeo about Trump’s meeting with North Korean leader Kim Jong Un in Singapore last month. Senator Edward Markey, Democrat of Massachusetts, expressed concern that there is ‘‘no verifiable evidence that North Korea . . . is denuclearizing.’’

‘‘I am afraid at this point that the Trump administration is being taken for a ride,’’ he said.

‘‘Fear not, senator,’’ Pompeo responded.