Sen. John McCain at the opening of the 53rd Munich Security Conference in Munich, Germany, on February 17. REUTERS/Michael Dalder Republican Sen. John McCain issued a blistering statement Tuesday morning condemning President Donald Trump's reported disclosure of classified information to Russian diplomats during a meeting in the Oval Office last week.

"The reports that the president shared sensitive intelligence with Russian officials are deeply disturbing," said the Arizona senator, who is notably hawkish on Russia.

"Reports that this information was provided by a US ally and shared without its knowledge sends a troubling signal to America's allies and partners around the world and may impair their willingness to share intelligence with us in the future."

The Washington Post reported Monday night that Trump "jeopardized a critical source of intelligence on the Islamic State" in his conversation with Russian Foreign Minister Sergey Lavrov and Ambassador Sergey Kislyak last week. The Post said Trump shared information that "had been provided by a US partner through an intelligence-sharing arrangement considered so sensitive that details have been withheld from allies and tightly restricted even within the US government."

The report drew bipartisan criticism from members of Congress. A spokesman for House Speaker Paul Ryan, who is normally tight-lipped about Trump's behavior, said Ryan "hopes for a full explanation of the facts from the administration."

Republican Sen. Bob Corker also weighed in, telling USA Today that "to compromise a source is something that you just don't do." He continued: "That's why we keep the information that we get from intelligence sources so close ... to prevent that from happening."

McCain criticized Trump's decision to spend time "sharing sensitive information with the Russians" instead of "focusing on Russia's aggressive behavior, including its interference in American and European elections, its illegal invasion of Ukraine and annexation of Crimea, its other destabilizing activities across Europe, and the slaughter of innocent civilians and targeting of hospitals in Syria.”

Jim Jeffrey, a former US ambassador who served as deputy national security adviser in the George W. Bush administration, made a similar characterization: "Whatever the president shared with the Russians beyond the absolute minimum raises the specter that he doesn't get how justifiably outraged Americans are at the hacking of the 2016 election. That's the most troubling."

The incident happened last Wednesday, one day after Trump fired the FBI director, James Comey, amid an FBI investigation into whether the Trump campaign colluded with Russians to undermine Hillary Clinton, then the Democratic presidential nominee, in the 2016 election.

Many have noted that Trump, as president, is legally allowed to essentially disclose classified information to whomever he wants. But the fact that the information he shared was not a US secret, but that of an American ally, may complicate his authority to declassify information at will. Matthew Rosenberg of The New York Times told CNN on Monday that the intel came from a close "Middle Eastern ally."

National security experts reacted with alarm to the report, calling it "appalling," "nauseating," and "mind-boggling."

"This is not a garden variety breach," national security experts, including Susan Hennessey and Benjamin Wittes, wrote for Lawfare on Monday. "And outrage over it is not partisan hypocrisy about protecting classified information."