Normalised relations with Cuba will give the US its best chance to influence the communist-ruled island, President Barack Obama said, urging Congress to ease the US economic embargo against Havana.

Obama, who announced on Wednesday that Washington was restoring diplomatic relations with Havana, said the historic end of decades of hostility between the two countries would not bring quick changes but ultimately would lead to greater freedom for the Cuban people.

Ultimately we need to go ahead and pull down the embargo

“What I know deep in my bones is that if you’ve done the same thing for 50 years and nothing has changed you should try something different,” Obama told reporters in an end-of-year news conference, referring to Washington’s long-held policy of trying to force Cuba to change by isolating it.

“This gives us an opportunity for a different outcome,” he said. “Because suddenly, Cuba is open to the world in ways that it has not been before.”

In addition to announcing the US will reestablish diplomatic relations with Cuba, Obama also said his administration will undertake a series of measures to ease restrictions on commerce, transportation and banking.

But the biggest obstacle to normal ties with Cuba is a more than 50-year economic embargo that is enshrined in law, most notably in the Helms-Burton act passed in 1996, and that would have to be lifted by Congress.

Republicans, who will control both chambers of Congress in January after their midterm election gains last month, have vowed to block any effort to ease the embargo and say they will try to slow the normalisation by blocking funds for an embassy and the confirmation of an ambassador.

Obama said he would be willing to weigh in with Congress but he expected the debate over ending the embargo would unfold over time.

“I think that ultimately we need to go ahead and pull down the embargo, which I think has been self-defeating in advancing the aims that we’re interested in. But I don’t anticipate that happening right away,” he said.