William Burns, the director of the Central Intelligence Agency, told the US Senate on Wednesday that Russia has amassed sufficient military forces and equipment on the border of Ukraine to allow a Russian incursion into the country.
Mr Burns expressed serious concern over the ongoing Russian military build-up in the Crimea and Donbass region over the past four weeks.
The CIA director, a former ambassador to Russia, said that experience taught him "not to underestimate the ways in which President [Vladimir] Putin and the Russian leadership can throw its weight around".
“The Russian military build-up in Crimea and alongside the border of the Donbass is a serious concern,” Mr Burns told the Senate Intelligence Committee.
The build-up, in which forces, tanks and military vehicles were sent to the border, carries more than one signal, he said.
It could be, Mr Burns said, “signalling a way to intimidate the Ukrainian leadership, signalling to the United States – but also that build-up has reached a point that it could provide the basis for limited military incursions [into Ukraine] as well. It is something that not only the United States but also our allies have to take very seriously”.
Alongside Director of National Intelligence Avril Haines, FBI director Chris Wray, director of the National Security Agency Gen Paul Nakasone and director the Defence Intelligence Agency Gen Scott Berrier, Mr Burns told the Senate that US intelligence agencies were exchanging information with European allies on the escalation and that part of the purpose for President Joe Biden's call to Mr Putin on Tuesday was to "register very clearly the seriousness of our concern".
The White House said that Mr Biden “emphasised the United States’ unwavering commitment to Ukraine’s sovereignty and territorial integrity”.
“The president voiced our concerns over the sudden Russian military build-up in occupied Crimea and on Ukraine’s borders, and called on Russia to de-escalate tension.”
After the call, footage was released of more Russian military vehicles heading towards the border amid reports of shelling at Donetsk in Ukraine.
Mr Austin announced an increase of US personnel in Germany by 500 troops this autumn as a means to protect shared interests.
Mr Burns and the intelligence directors' testimony took place after the release of the US threat assessment report for 2021.
The 27-page-report highlights Moscow’s expansionist ambitions in Eastern Europe.
“In the former Soviet Union, Moscow is well positioned to increase its role in the Caucasus, intervene in Belarus if it deems necessary and continue destabilisation efforts against Ukraine while settlement talks remain stalled and low-level fighting continues,” the report said.
The report also prioritises China’s threat and increasing global rivalry with the US. Mr Wray told the Senate committee that the FBI has thousands of current investigations linked to Beijing.
“We're opening a new investigation into China every 10 hours and I can assure the committee that's not because our folks don't have anything to do with their time," the FBI director said.
“We have now over 2,000 investigations that tie back to the Chinese government,” he said.