President Joe Biden said the US has "not yet verified" Russia's claim that some of its forces have withdrawn from the Ukraine border and said an invasion of Ukraine remains a distinct possibility.
Biden made the remarks at the White House hours after Russia announced that some units participating in military exercises near Ukraine's borders would begin returning to their bases. Russian President Vladimir Putin earlier Tuesday said Russia was ready for talks with the United States and NATO on military transparency, missile deployment limits and other security issues.
But Biden continued to express scepticism about Russia's intentions. Biden warned again that if Russia invades Ukraine the US "will rally the world to oppose its aggression."
A cyberattack has hit the websites of Ukrainian government agencies and major banks, Ukrainian authorities say.
The attack on Tuesday (Wednesday NZT), the latest of several hacking operations targeting Ukraine, came after weeks of escalating fears that Russia might invade.
Russia sent signals on Tuesday that it might be pulling back from the brink of an invasion, but Western powers demanded proof.
At least 10 Ukrainian websites stopped working because of DDOS attacks, including those of the Defence Ministry, Foreign Ministry, Culture Ministry and Ukraine's two largest state banks.
Customers at Ukraine's largest state-owned bank, Privatbank, and the state-owned Sberbank reported problems with online payments and the banks' apps.
"There is no threat to depositors' funds," the Ukrainian Information Ministry's Centre for Strategic Communications and Information Security said. The deputy minister, Victor Zhora, confirmed a cyberattack.
The ministry suggested Russia could be behind the attacks without providing details. "It is possible that the aggressor resorted to tactics of petty mischief, because his aggressive plans aren't working overall," the statement said.
Ukraine last month accused Russia of being behind a cyberattack that temporarily disabled about 70 Ukrainian government websites simultaneously. Ukrainians were warned to "be afraid and expect the worst".
Russia launched one of the most devastating cyberattacks on Ukraine in 2017 with the NotPetya virus, causing more than US$10 billion ($15b) in damage worldwide. The virus, also disguised as ransomware, was a so-called "wiper" that scrubbed entire networks.
The United States has accused Moscow publicly of preparing to invade Ukraine and underscored that cybersecurity remains a pivotal concern.