MEXICO CITY — The Cuban government has released 53 dissidents it had promised to free under the accord with Washington to restore diplomatic relations and step up economic exchanges, United States officials said Monday.

The release of the last prisoners on the list was seen as an important indicator of the Cuban government’s commitment to carrying out the agreement, which was announced by President Obama and the Cuban president, Raúl Castro, on Dec. 17.

Yet it was received with skepticism by Cuban opposition figures, who said the government had released fewer prisoners than the numbers suggested.

It came less than two weeks before Roberta S. Jacobson, the assistant secretary of state for Western Hemisphere affairs, is to arrive in Cuba for talks on Jan. 21 and 22. The discussions are to focus on migration issues but will also be used to discuss the restoration of full diplomatic relations.