But Mr. McFaul said Mr. Putin would welcome Mr. Trump’s odd claim that the special counsel, Robert S. Mueller III, is fomenting anti-Russian sentiment in the United States.

More than anything, however, Mr. McFaul said the Russians would view Mr. Trump’s scattershot approach as weakness.

“My sense is that the Kremlin has given up on their previous hope that Trump might repair relations because he is not focused and not in control of foreign policy making,” he said.

On Syria, Mr. Trump’s promise of a coming missile strike not only violated his own promise never to predict such action — it also put him ahead of America’s allies. While France has been steadfast in its support for strikes, the British government is still deliberating. The administration, officials said, would like its allies to be part of a united front.

As a practical matter, Mr. Trump’s foreshadowing might enable Mr. Assad to move some aircraft to get them out of the way of a missile strike. But analysts said any such movement would not alter the outcome, given the military superiority of the United States.

“We can pick off his equipment at will,” said Andrew J. Tabler, an expert on Syria at the Washington Institute for Near East Policy.

The lack of swift action after Mr. Trump’s tweet, however, could add to the perception of a White House not in sync. It comes after a week in which the president at first pushed for a rapid withdrawal of American troops from Syria — only to later acquiesce grudgingly to his generals, who argued that the troops should remain in the country for a few more months to train local forces and stabilize Syrian towns liberated from the Islamic State.