WASHINGTON - President Donald Trump came under pressure on Tuesday from lawmakers, including some of his fellow Republicans, to give a fuller explanation of why he revealed highly sensitive intelligence information to senior Russian officials at a White House meeting last week.

Officials said Trump discussed intelligence about Islamic State with Russian Foreign Minister Sergei Lavrov and Russian Ambassador Sergei Kislyak at last Wednesday's talks in the Oval Office.

The information had been supplied by an ally in the fight against the militant group, the officials said. The New York Times, The Wall Street Journal and CNN identified the ally as Israel but two U.S. national security sources said they doubted that. Israeli officials declined to comment.

The White House declined to comment on Tuesday. This includes press secretary Sean Spicer, who also declined to say whether the White House would share transcripts of Trump's meeting with Lavrov with lawmakers who have asked for them.

The disclosure of Trump's discussion rocked the administration as it struggled to move past the backlash over Trump's abrupt firing on May 9 of FBI Director James Comey, whose agency is investigating potential ties between Russia and Trump's 2016 presidential campaign.

Trump said on Twitter on Tuesday he had an "absolute right" to share facts with Russia, adding he wanted Moscow to be more active in fighting Islamic State militants.

The Senate Intelligence Committee has asked the White House for more information about reports that Trump gave intelligence information to the Russians, a spokeswoman for the panel said.

Congressional investigators are expected to seek copies of any notes taken during the meeting, a congressional source said.

Trump's main guest at last week's meeting was Lavrov, the leading promoter of Russian foreign policies that are often sharply at odds with U.S. aims in Syria and Europe.

While not unprecedented, it is rare for a foreign minister to be granted bilateral talks in the inner sanctum of the White House with a U.S. president as Lavrov was.

Trump repeatedly called during his campaign for improved U.S. relations with Russia, damaged by years of disagreement over Russia's role in Ukraine and its backing for Syrian President Bashar al-Assad.

But his ties with Russia have clouded the early months of his presidency. Along with the FBI probe, congressional committees are investigating alleged Russian meddling in the election and whether there was any collusion by the Trump campaign.

A U.S. president has the authority to disclose even the most highly classified information at will, but U.S. and allied officials said that by giving information to Russia, Trump had endangered cooperation from an ally that has intelligence on Islamic State.

U.S. Representative Barbara Comstock, a Republican, called for immediate classified briefings for lawmakers "so that Congress can at least know as much as Russian leaders."

"Anything you give the Russians, you have to assume the worst, not the best," Republican Senator Lindsey Graham told Fox News. "So clearly the president didn't do anything illegal. But my advice to the president would be if you're going to talk to the Russians about anything sensitive, run it through the system first."

National security adviser H.R. McMaster said Trump did not know the source of the information he disclosed to the Russians so could not have compromised the U.S. ally.

"What the president shared was wholly appropriate," he said.

The two top Republicans in Congress, House Speaker Paul Ryan and Senate Majority Leader Mitch McConnell, were muted in their responses to Trump giving information to Russia. Ryan's office said he hoped for a full explanation.

Asked if he had concerns about Trump's handling of classified information, McConnell answered, "No."

The top Democrat in the Senate, Chuck Schumer, called on the White House to make transcripts of the Oval Office meeting with the Russians available.

Representative Elijah Cummings, the senior Democrat on the House of Representatives Oversight and Government Reform Committee, said Trump's disclosure only reinforced Democrats' call for an independent investigation into alleged ties with Russia.

"I would hope that at some point the Republicans will join with the Democrats and say, 'Look, we've got to address this.' This is indefensible," Cummings told MSNBC.

Turmoil in the White House in recent weeks has overshadowed legislative priorities such as healthcare and tax reform eyed by Trump and his fellow Republicans who control Congress.

The euro surged more than 1 percent against a broadly weaker dollar on Tuesday, rising to its highest since Trump was elected president in November. Weaker-than-expected U.S. housing data also dampened the dollar.

Controversy over Russia has also laid bare sharp divisions between the White House and U.S. intelligence agencies, which concluded in January that Russia had tried to influence the election in Trump's favor. Moscow denies that.

During the presidential campaign Trump repeatedly assailed his Democratic rival, Hillary Clinton, for her handling of classified information by email while she was secretary of state. The FBI concluded after an investigation last year that there were no grounds to pursue any charges against Clinton.

Trump departs on Friday for his first overseas trip as president, traveling to Saudi Arabia, Israel, Italy and Belgium on visits that will test his foreign policy skills.

DEFENDING TRUMP

The Kremlin came to Trump's defense on Tuesday, calling reports that he had disclosed classified material in the White House meeting as "complete nonsense."

Trump's secretary of state, Rex Tillerson, and national security adviser, H.R. McMaster, issued statements saying no sources, methods or military operations were discussed at the Russian meeting.

McMaster said the story, initially reported by The Washington Post, was false.