The intelligence committee meets Tuesday afternoon in a previously scheduled closed session, but senators on the panel say they expect Trump's meeting to Russian officials to be an issue that's raised. He also tried to cast it as a generous and wise move.
Afterward, White House officials took steps to contain the damage, placing calls to the CIA and the National Security Agency, the newspaper said. The report uses unnamed sources, "current and former US officials", as the basis of the accusations.
The Trump administration immediately rejected the claims as "false".
Speaking to reporters at the White House a day later, the Army general said Trump shared "wholly appropriate" information.
The Post story - which The New York Times confirmed but NBC News has not - did not report that Trump shared sources and methods, but that sharing information provided by an ally with the expectation of secrecy threatened future intelligence-gathering operations.
A US president has the authority to disclose even the most highly classified information at will, but multiple USA and allied officials told Reuters that Trump had endangered cooperation from an ally that has some intelligence on Islamic State.
The last week meeting between Trump, Lavrov and Kislyak had already raised alarm bells in Washington, primarily because it came one day after Trump chose to fire FBI Director James Comey while the bureau investigated the President campaign's alleged ties to Russian Federation.
Trump's contradiction of the Russian spokeswoman also appeared to catch his biggest boosters, the cast of "Fox and Friends", by surprise, as the historian Keven Kruse noted. The administration told the media that Comey was let go after seeking the recommendation of top Justice Department officials, but Trump eventually told NBC News' Lester Holt that he planned to fire Comey all along.
The White House's botched handling of Trump's firing last week of FBI Director James Comey, who was overseeing the bureau's Russian Federation probe, and the president's own volatile statements about his actions are also likely to raise questions among allies about the USA leader's standing.
The President made his first statement on Twitter following a series of denials from White House officials. Chuck Schumer is calling on the White House to provide the transcript of President Donald Trump's meeting with Russian diplomats to the congressional intelligence committees "as soon as possible".
Hayes and Meghan McCain noted that McMaster said intelligence sources and methods were not "discussed" in the meeting. The Trump administration barred American journalists from this meeting. He drew a distinction between leaks and Trump's conversation with the Russians, saying the discussion with the Russian officials involved shared threats to the USA and Russia.
"We don't say what's classified, what's not classified", McMaster said.
Editor's Note: Julie Pace has covered the White House and politics for The Associated Press since 2007. He said Trump discussed a range of subjects with the Russians, including "common efforts and threats regarding counter-terrorism". Some of the leaders he'll meet come from countries the US has intelligence-sharing agreements with. The information had been obtained by a USA partner and shared with Washington, according to the official.