According to US Secretary of State Antony Blinken, a Russian invasion of Ukraine “could begin at any time,” including during the Beijing Winter Olympics, and the US continues to “see very troubling signs of Russian escalation, including new forces arriving at the Ukrainian border.”

Following a day of meetings in Melbourne, the top US diplomat made the remarks alongside his Quad counterparts – Australia, India, and Japan – and after the State Department and President Joe Biden warned US citizens to leave Ukraine immediately.

“As we’ve said before, we’re in a period where an invasion could start at any time – and to be clear, that includes during the Olympics,” Blinken said.

Prior to the start of the Olympics earlier this month, Deputy Secretary of State Wendy Sherman suggested that the Winter Games, which are being hosted by China, might influence Russian President Vladimir Putin’s thinking about the timing of an invasion. Putin visited Beijing for the start of the Olympics, where he met with Chinese President Xi Jinping. The two signed a lengthy agreement pledging unrestricted cooperation.

At the joint news conference on Friday, Blinken told reporters that the US was “continuing to draw down our embassy” in the Ukrainian capital of Kyiv and “will continue that process.”

“We’ve also been very clear that any American citizens who are still in Ukraine should leave immediately,” he added.

On Thursday night, the White House convened a meeting in the Situation Room with several Cabinet members and senior national security officials to discuss Russia’s ongoing military buildup near Ukraine, according to two officials familiar with the matter. According to one of the sources, there have been several Situation Room meetings in recent weeks and months to discuss the brewing crisis, but the meetings have become more urgent in recent days as Russia has continued to move forces, weapons, and logistical equipment into the area and increased troop readiness.

At 11:00 a.m. ET on Friday, Biden will hold a conference call with other world leaders to discuss the situation in Ukraine. According to the official, the leaders of Canada, the United Kingdom, France, Germany, Italy, Poland, Romania, NATO, the European Commission, and the European Council will be on the call.

The State Department authorized the departure of non-emergency personnel from the US Embassy in Kyiv last month and ordered family members to leave the country, and on Thursday it issued a new travel advisory advising American citizens in Ukraine to “depart now via commercial or private means.”

Although the Quad discussions on Friday were primarily focused on the Indo-Pacific region, Russia’s aggression toward Ukraine was discussed among the four foreign ministers.

The top US diplomat repeatedly noted that the crisis goes deeper than the physical threat posed by Russia to Ukraine and could undercut the international rules-based order that the Quad countries have vowed to uphold.

“What is at stake is not simply, as important as it is, Ukraine’s territorial integrity, sovereignty, and independence, but very basic principles that have, in a hard-fought way after two World Wars and a Cold War, undergirded security, peace, and prosperity for countries around the world — principles like one country cannot simply change another’s borders by force; principles like one country cannot simply dictate to another its choices, policies, and who it will associate with.”

Although the Biden administration is “relentlessly” focused on resolving the Russia-Ukraine crisis, his presence in Australia for the Quad meetings “underscores our commitment to staying focused on the Indo-Pacific,” according to Blinken.

State Department officials are busy preparing for a variety of potential meetings between US and Russian officials, which may or may not take place as concerns about a Russian invasion grow, according to two department officials.

A meeting between Biden and Putin, a meeting between Blinken and Russian Foreign Minister Sergey Lavrov, or lower-level meetings are all possibilities.

Blinken stated last month that the ball is in Russia’s court, and officials confirmed that this is still the case for future diplomatic engagements. The United States gave Moscow a written response aimed at deterring a Russian invasion of Ukraine more than two weeks ago, and is waiting for Russia’s response.