WASHINGTON — Under pressure from Republicans and Democrats, the Trump administration on Thursday turned over to Congress a list of Russia-connected entities it will use to determine new sanctions meant to rebuke Russia for actions in Eastern Europe, Syria and the 2016 United States presidential election.

Administration officials made clear to lawmakers that they intended to impose sanctions on individuals in the United States and elsewhere who did “significant” business with the Russian entities, sending an early warning that such deals must soon end.

The list appeared to be an attempt to mollify critics — including Senators John McCain, Republican of Arizona, and Benjamin L. Cardin, Democrat of Maryland — who said that the administration had not moved quickly enough to punish a key American adversary, using legislation passed by Congress in July and signed by President Trump in August. That legislation required that the administration produce the list of entities by Oct. 1.

Administration officials said the list, a copy of which was obtained by The New York Times, was not itself an imposition of sanctions, but rather the government’s assessment of organizations or persons “that are part of, or operating for or on behalf of, the defense or intelligence sectors of the government of the Russian Federation.”