President Vladimir V. Putin of Russia agreed on Tuesday during a phone call with President Trump to halt strikes on Ukrainian energy infrastructure, the Kremlin said in a statement, but restated his concerns about a broader 30-day cease-fire that the United States and Ukraine had agreed upon and proposed to Russia.

The result seemed to fall short of what Mr. Trump had been hoping for in his outreach to Moscow, after several days of optimistic-sounding pronouncements from the White House that peace was within reach.

During the call, Mr. Putin said his “key condition” to end the conflict and prevent it from escalating was a “complete cessation” of foreign military and intelligence assistance to Kyiv, the Kremlin said.

It was unclear how Ukraine would respond to the Kremlin’s statement: it falls short of the unconditional 30-day U.S.-backed cease-fire proposal that Ukraine had already said it would support.

Ukrainian officials have accused Mr. Putin of playing for time in order to maintain leverage in negotiations, and allow Russia time to continue bombarding Ukrainian cities and towns.

This is a developing story.