WASHINGTON — President Joe Biden on Friday vowed to make it “very, very difficult” for Russian President Vladimir Putin to take military action in Ukraine, saying his administration is putting together a comprehensive set of initiatives to curb Russian aggression.

The president offered the measured warning to Putin amid growing concern about a Russian buildup of troops on the Ukrainian border and increasingly bellicose rhetoric from the Kremlin.

“What I am doing is putting together what I believe to be will be the most comprehensive and meaningful set of initiatives to make it very, very difficult for Mr. Putin to go ahead and do what people are worried he may do,” Biden told reporters.

There are signs that the White House and Kremlin are close to arranging a conversation next week between Biden and Putin. Putin’s foreign affairs adviser Yuri Ushakov told reporters Friday that arrangements have been made …