Vladmir Putin is expected to make a 'big announcement' during a military parade for Russia's Victory Day on Monday, Western officials said on Friday.
They have speculated he may use the annual celebration marking Russia's victory over Nazi Germany in 1945 to declare mass mobilisation or state that he is widening the conflict in Ukraine.
Parades are planned for Red Square in Moscow and other cities across the country on May 9.
No foreign leaders have been invited to the event this year following worldwide condemnation of Russia's invasion of Ukraine.
Western officials said on Friday that they could not rule out Putin using the occasion to officially declare Russia's involvement in Ukraine a war.
"Of course there's also questions about mass mobilisation and various other things," one Western official added.
"We're not seeing signs that something like that is really being prepared. Of course the Kremlin has denied it. [But] the Kremlin denied the invasion [of Ukraine] and then it happened.
"Our expectation is, there's more likely to be more gradual steps but, there may well be some big eye catching announcement on Monday."
Ukrainian president Volodymyr Zelensky has invited German Chancellor Olaf Scholz for talks in Kyiv, suggesting the visit could also take place on Russia’s annual Victory Day.
Speaking at an event held by the Chatham House think tank, the Ukrainian president said the move would be a “very powerful political step”.
Asked whether Ukraine was satisfied with the support it was getting, particularly from EU nations including Germany, and what he would say to Mr Scholz if he had the chance to speak with him, Mr Zelensky said: “You cannot be slightly evil and slightly good.
“With the right hand you impose sanctions, with the left hand you sign the Russian contracts. This is not right. This is hypocrisy.”
It comes amid rumours about Putin's deteriorating health as the Russian president continues to further cut his people off from outside communication.
"I'm afraid the campaign of internal repression has continued," a western official said.
"There are more and more controls. Any independent media has now been suspended.
“There have been more controls introduced on access to social media.
“More and more of those who had been independent thinkers are being labelled foreign agents and frozen out.
“It makes it really difficult at the moment to gauge what the Russians really think."
Commenting on rumours that Putin is suffering from an agressive cancer, they added: "There are a lot of rumours about lots of things at the moment.
“President Putin is going to be 70 this year. This is a system that is not going to give us health bulletins."
