WASHINGTON — After Russian forces seized three Ukrainian ships in November and threatened to turn the Sea of Azov into a Russian lake, Trump administration officials outlined possible responses like imposing additional sanctions, sending ships to make port calls or deploying monitors.

Two months later, President Trump has not taken significant action despite widespread support within his administration, nor have the European allies. In Moscow, President Vladimir V. Putin’s Kremlin, rather than being deterred, has grown so emboldened that it is talking again about dismantling Ukraine as an independent state.

Mr. Trump’s approach toward Russia has attracted new attention with recent reports that the F.B.I. in 2017 opened a counterintelligence investigation into whether the president was acting on Russia’s behalf, that he has gone to unusual lengths to conceal the details of his meetings with Mr. Putin and that he threatened to pull out of NATO. The president’s lawyer revealed on Sunday that Mr. Trump’s proposed skyscraper in Moscow was under discussion all the way through the November 2016 election.

Mr. Trump has adamantly insisted that there was “no collusion” with Moscow during his campaign and that he has never worked for Russia. He regularly tries to dispel suspicions by declaring that he has done more to counter Russian aggression than other recent presidents have. “I have been FAR tougher on Russia than Obama, Bush or Clinton,” he wrote on Twitter a week ago.