MEXICO CITY — The United States and Cuba appear to be edging closer to an agreement to restore full diplomatic ties, with President Raúl Castro of Cuba saying Tuesday that his country was ready to exchange ambassadors once it was formally removed this month from the American government’s list of states sponsoring terrorism.

President Obama announced in April that he would remove Cuba from the list 30 years after it was added for supporting leftist insurgencies. He has called the designation outdated, and it has been a major stumbling block to the goal of restoring relations that he and Mr. Castro jointly declared in December. The law requires a 45-day review period for removal from the list, which would take effect on May 29.

Mr. Castro, speaking to reporters at the Havana airport as President François Hollande of France ended a visit, said of the terrorism designation, “This sort of unjust accusation is about to be lifted, and we’ll be able to name ambassadors.”

Still, it was unclear how fast that would occur, and the two governments do not yet appear to have agreed on resolving all of their concerns.