The classified intelligence that President Trump disclosed in a meeting last week with Russian officials at the White House was provided by Israel, according to a current and a former American official familiar with how the United States obtained the information. The revelation adds a potential diplomatic complication to the episode.
Israel is one of the United States’ most important allies and a major intelligence collector in the Middle East. The revelation that Mr. Trump boasted about some of Israel’s most sensitive information to the Russians could damage the relationship between the two countries. It also raises the possibility that the information could be passed to Iran, Russia’s close ally and Israel’s main threat in the Middle East.
Israeli officials would not confirm that they were the source of the information that Mr. Trump shared. In a statement emailed to The New York Times, Ron Dermer, the Israeli ambassador to the United States, reaffirmed that the two countries would maintain a close counterterrorism relationship.
“Israel has full confidence in our intelligence-sharing relationship with the United States and looks forward to deepening that relationship in the years ahead under President Trump,” Mr. Dermer said.
In the meeting with the Russian ambassador and foreign minister, Mr. Trump disclosed intelligence about an Islamic State terrorist plot. At least some of the details that the United States has about the plot came from the Israelis, the officials said.
The officials, who were not authorized to discuss the matter and spoke on the condition of anonymity, said that Israel previously had urged the United States to be careful about the handling of the intelligence that Mr. Trump discussed.
Mr. Trump said on Tuesday on Twitter that he had an “absolute right” to share information in the interest of fighting terrorism and called it a “very, very successful meeting” in a brief appearance later Tuesday at the White House alongside President Recep Tayyip Erdogan of Turkey. Lt. Gen. H. R. McMaster, Mr. Trump’s national security adviser, told reporters that he was not concerned that information sharing among intelligence partners would stop.
“What the president discussed with the foreign minister was wholly appropriate to that conversation and is consistent with the routine sharing of information between the president and any leaders with whom he’s engaged,” General McMaster said at a White House briefing, seeking to play down the sensitivity of the information Mr. Trump disclosed.
General McMaster added that the president, who he said was unaware of the source of the information, made a spur-of-the-moment decision to tell the Russians what he knew.
But General McMaster also appeared to acknowledge that Thomas P. Bossert, the assistant to the president for Homeland Security and counterterrorism, had called the C.I.A. and the National Security Agency after the meeting with the Russian officials. Other officials have said that the spy agencies were contacted to help contain the damage from the leak to the Russians.
General McMaster would not confirm that Mr. Bossert made the calls but suggested that if he did, he was acting “maybe from an overabundance of caution.”
“I have not talked to Mr. Bossert about that, about why he reached out,” General McMaster said.
Former officials said it was not uncommon for presidents to unintentionally say too much in meetings and said that in administrations from both parties, staff members typically established bright lines for their bosses to avoid crossing before such meetings.
Israel’s concerns about the Trump White House’s handling of classified information were foreshadowed in the Israeli news media this year. Newspapers there reported in January that American officials warned their Israeli counterparts to be careful about what they told the Trump administration because it could be leaked to the Russians, given Mr. Trump’s openness toward President Vladimir V. Putin.
“The Russians have the widest intelligence collection mechanism in the world outside of our own. They can put together a good picture with just a few details,” said John Sipher, a 28-year veteran of the C.I.A. who served in Moscow in the 1990s and later ran the C.I.A.’s Russia program for three years. “They can marry President Trump’s comments with their own intelligence, and intelligence from their allies. They can also deploy additional resources to find out details.”
The episode could have far-reaching consequences, Democrats warned. Any country that shares intelligence with American officials “could decide it can’t trust the United States with information, or worse, that it can’t trust the president of the United States with information,” said Representative Adam B. Schiff of California, the top Democrat on the House Intelligence Committee.
“I have to hope that someone will counsel the president about just what it means to protect closely held information and why this is so dangerous, ultimately, to our national security,” Mr. Schiff said at a policy conference in Washington sponsored by the Center for American Progress, a liberal group.