The Pentagon was aware that Russian forces had been flown into Crimea late last week, days before they took control of military installations and a ferry terminal on the peninsula, officials told NBC News — but it "was not clear what they intended to do, or when," according to one senior official.
Several Il-76 military cargo planes flew an undetermined number of forces into Crimea late last week, according to the officials. And U.S. intelligence "kept close watch" on the situation for days, according to one official.
"We know something was going down, but didn't know what," the official said.
U.S. officials who spoke to NBC News stressed that there were "no signs" this would be a major military operation with heavy armament or equipment.
Russian officials continue to insist the armed forces are "civilian militia," not military — despite intelligence that the forces were flown into Crimea aboard Russian military aircraft.
Defense Secretary Chuck Hagel testified Wednesday before the Senate Armed Services Committee that "early last week we were made aware of this threat."
Hagel said the information came up at the NATO-Ukraine meeting in Brussels last Wednesday. He did not elaborate, citing intelligence matters.
Sen. John McCain reportedly fired back in a testy exchange.
"The fact is, Mr. Secretary, it was not predicted by our intelligence, and that's already been well-known, which is another massive failure because of our misreading — total misreading of the intentions of Vladimir Putin," McCain said, based on media reports.
A CIA spokesman late Wednesday said that the agency has kept members of Congress updated since the Ukraine crisis began.
"Since the beginning of the political unrest in Ukraine, the CIA has regularly updated policymakers to ensure they have an accurate and timely picture of the unfolding crisis," CIA spokesman Todd Ebitz said. "These updates have included warnings of possible scenarios for a Russian military intervention in Ukraine. Any suggestion otherwise is flat wrong."
The Russians did give the U.S. 24-hour notice before they conducted a "snap-exercise" with thousands of Russian troops along the Ukraine border last week, U.S. officials told NBC News.
— Jim Miklaszewski and Courtney Kube