Russia could invade Ukraine before the Beijing Winter Olympics end on February 20, National Security Advisor Jake Sullivan has said. He gave the warning at a press briefing in the White House on February 11.

Russian forces were continuing to arrive at the border with Ukraine and an invasion could happen at any moment, Sullivan said. “It could begin during the Olympics, despite a lot of speculation that it would only happen after the Olympics.”

Any Americans in Ukraine should leave immediately, "in the next 24 to 48 hours," Sullivan said. "If a Russian attack on Ukraine proceeds, it is likely to begin with aerial bombing and missile attacks that could, obviously, kill civilians without regard to their nationality," he added.

Sullivan's remarks can be seen at the White House website and YouTube channel.

The U.S. ordered the evacuation of its Kyiv embassy staff on February 12, according to CNN and other news outlets.

No final decision from Putin

Sullivan was asked to comment on a PBS "NewsHour" report stating that Russian President Vladimir Putin had decided whether to invade and the Russian military had been notified of his decision. "We have not seen anything come to us that says a final decision has been taken," Sullivan said.

Warning against a false-flag pretext for war

The National Security Advisor said the Biden Administration was "firmly convinced" that if an invasion were to occur, Russia would first consider staging a false-flag operation "to blame on the Ukrainians as a trigger for military action." Sullivan said the Biden Administration was discussing this openly to prevent the international community from accepting such a bogus justification for war.

Biden gave Ukraine $650 million in military aide

Sullivan noted that President Joe Biden had provided Ukraine with "more than half a billion dollars – $650 million – in defensive assistance to Ukraine." He stressed that the weapons given to Ukraine were defensive in nature and not intended "for offensive purposes against any country."

American soldiers in Germany, Poland and Romania were only there to defend NATO countries, Sullivan said.

President Biden would consider sending more military forces "as circumstances warrant," he said, adding that they would not be sent to Ukraine. "They are not going to war with Russia," he stressed.

Kamala Harris to meet with allies in Munich

It was noted at the press briefing that Vice President Kamala Harris would attend the February 18-20 Munich Security Conference.

Sullivan was asked whether it would not be better if Biden himself went to Munich. Sullivan said the Biden Administration had held "countless" meetings, phone calls and video conferences with foreign leaders about the crisis in Ukraine. He dismissed suggestions that the President was not doing enough to stop an invasion.

In an effort to complicate Russian preparations for a possible invasion of Ukraine, the Biden Administration had been releasing intelligence information at a brisk rate unseen since the 1962 Cuban missile crisis, The New York Times reported. The paper said the Biden Administration's use of intelligence information was also reminiscent of the way President George W. Bush had justified going to war against Iraq in 2003.

At the press briefing, Sullivan pointed out that Bush had used the public disclosure of intelligence to start an invasion, but Biden was using it to stop one.