WASHINGTON (NewsNation Now) — A Russian invasion of Ukraine could come within the week, the White House said Friday, urging Americans to leave the country now. The president also ordered an additional 3,000 U.S. troops to Poland.

National security adviser Jake Sullivan said the U.S. still did not know if Russian President Vladimir Putin had made a decision to invade, but that all the elements are now in place for a rapid invasion. Sullivan said Russia could invade in the next two days, even before the end of the Winter Olympics on Feb.20.

“We are not saying that a decision has been taken by President Putin,” Sullivan said during a press briefing Friday. “What we are saying is that we have a sufficient level of concern based on what we are seeing on the ground, and what our intelligence analysts have picked up, that we are sending this clear message.”

Sullivan said all the pieces were in place for a major military operation that could start “rapidly.”

“The risk is high enough and the threat is now immediate enough that prudence demands that it is the time to leave now,” Sullivan said.

Sullivan said the United States is ready to continue with “results-oriented diplomacy” that addresses U.S., Russian and European security concerns, but it is also ready to respond decisively with European allies should Russia take military action.

Part of the United State’s response would include severe economic sanctions, with similar ones imposed by the European Union, United Kingdom, Canada and other countries.

It would also include changes to NATO and American Force posture along the eastern flank of NATO, Sullivan said.

Several NATO allies including Britain, Canada, Norway and Denmark also are asking their citizens to leave Ukraine, as is non-NATO ally New Zealand.

But while the U.S will continue to support Ukraine, Sullivan said, it will not be sending its own troops there to help Americans evacuate.

“The president will not be putting the lives of our men and women in uniform at risk by sending them into a war zone to rescue people who could have left now but chose not to,” Sullivan said.

However, a senior defense official said Defense Secretary Lloyd Austin ordered 3,000 soldiers from the 82nd Airborne Infantry Brigade Combat Team to Poland. They will depart over the next couple of days, the official said.

The senior defense official added that the additional deployments are temporary in nature.

Ukraine’s military chief, Valerii Zaluzhnyi, told Ukrainian President Volodymyr Zelenskyy that authorities plan to engage 1.5 million to 2 million people in training for the army reserve.

Russia scoffed at the U.S. talk of urgency.

“The hysteria of the White House is more indicative than ever,” said Russian Foreign Ministry spokeswoman Maria Zakharova. “The Anglo-Saxons need a war. At any cost. Provocations, misinformation and threats are a favorite method of solving their own problems.”