WASHINGTON — The Trump administration on Wednesday tightened the economic embargo on Cuba, restricting Americans from access to hotels, stores and other businesses tied to the Cuban military.

A lengthy list of rules, which President Trump promised in June to punish the communist government in Havana, came just as Mr. Trump was visiting leaders of the communist government in Beijing and pushing business deals there. Wednesday’s announcement was part of the administration’s gradual unwinding of parts of the Obama administration’s détente with the Cuban government.

Americans wishing to visit Cuba will once again have to go through authorized tour operators, and tour guides will have to accompany the groups — making such trips more expensive.

People who already have booked and paid for a trip on their own will be allowed to go, and transactions with businesses on the barred list can be completed, the administration said. The new rules, which go into effect Thursday, apply only to future travel and commerce. Eighty-three hotels are on the banned list.