U.S. intelligence officials, who had been pushing to dismantle Moscow's spy networks, believed that the president might decide against a recommendation to close the Russian Consulate in Seattle.

In conversations with European leaders, Donald Trump said the United States was not interested in expelling spies in response to the poisoning of a Russian spy if other countries were not doing the same.

But on Friday, the president's national security team presented him with three options, and Trump's final decision set in motion an exodus of 60 Russian spies - a surprising rebuke of Moscow that even caught U.S. allies off guard.

"We received signals that expulsions were coming, but the numbers surprised us," said a senior European diplomat based in Washington. "It was very high."

The uncertainty surrounding the president's decision reflected a phenomenon that has baffled the United States' closest allies for almost a year: Despite Trump's reliably warm rhetoric toward Moscow and his steadfast reluctance to criticize Russian President Vladimir Putin, the Trump administration has at multiple times taken aggressive action against Russia at the recommendation of the president's top aides.

"This fits the pattern of our policy toward Russia in the Trump administration," said John Herbst, a Russia scholar at the Atlantic Council. "If you just look at policy, this administration has taken steps the Obama administration was not willing to, such as supplying antitank missiles to Ukraine. The president's heart doesn't seem to be in it, but for whatever reason, he's willing to go along with his advisers."

The three options presented to the president: "light, medium and heavy."

The Monday announcement grew out of a push by U.S. allies and the intelligence community for a strong retaliatory response to the poisoning of Sergei Skripal and his daughter in Britain. Shortly after the attack, Fiona Hill , a National Security Council senior director, began leading policy coordination meetings that culminated in a pivotal Friday meeting that included Defense Secretary Jim Mattis, national security adviser H.R. McMaster, FBI Director Christopher Wray and Director of National Intelligence Daniel Coats, among other top officials.

The three options presented to the president were described as "light, medium and heavy" by one administration official, who like others spoke on the condition of anonymity to discuss sensitive deliberations.

The "light" option called for expelling roughly 30 spies while leaving the Seattle consulate intact, two U.S. officials said. The "medium" option, which the president ultimately chose, expelled 48 officials at the embassy in Washington and 12 at the U.N. mission in New York and shuttered the Seattle consulate.

U.S. officials declined to spell out the "heavy" option, to avoid previewing steps the president could take in response to Moscow's retaliation, but one official noted that U.S. counterintelligence is aware of well over 40 Russian spies operating in the United States who were not included in the initial purge. On Thursday, the Kremlin announced the expulsion of 60 U.S. officials.

During the meeting, the president's aides described the options to him in broad terms and did not give a precise number of spies for the "medium" scenario, leaving the head count to subordinates, one official said.

The official described the internal debate using boxing metaphors.

"If you go heavy now and the Russians really retaliate, we would be more limited in what we can do later," the official said. "With the medium option," the official said, "you're throwing a solid punch but withholding a fist, and the president was persuaded by that option."

Historically, a similar purge has not occurred since 1986, when the Reagan administration expelled 55 Russian officials. The George W. Bush administration purged 50 in 2001 in response to the Robert Hanssen espionage case.

Once the White House position became clear, U.S. officials including McMaster and Deputy Secretary of State John Sullivan began calling foreign leaders, with the number of commitments from other countries growing from 10 last Friday to 16 on Monday morning to more than 25 on Thursday.

The U.S. expulsion of 60 officials far outmatches moves taken by other countries, an outcome that was far from clear last week when Trump congratulated Putin on his reelection and neglected to raise the poisoning incident, despite the guidance of his advisers.

It remains unclear whether Moscow's purge will end the diplomatic imbroglio or fuel a further tit-for-tat between the two adversaries.

On Thursday, State Department spokeswoman Heather Nauert said the United States is "reviewing the details of the Russian action" and reserves the right to respond to "any Russian retaliation against the United States."