U.S. President Barak Obama, speaking at the close of the Summit of the Americas on Sunday said the relations between U.S. and Cuba need to be backed up by action not simply words.

We are not going to change our policy overnight, Obama said at a news conference.

Obama admitted that Washington's half century-old policy towards Cuba hasn't worked and urged Cuba to give more freedoms to its people.

Issues of political prisoners, freedom of speech and democracy are important, and can't simply be brushed aside, he said.

Those remarks dampened hopes of a quick end to a long-standing U.S. trade embargo on Cuba.

Last week, Obama made the historic acknowledgement on Cuban issues that led many to believe Washington and Havana might be on course to negotiate an end to the 47-year-old US embargo.

Obama and Cuban president Raul Castro in recent days said they were willing to open talks on such hot issues as political prisoners and human rights.

But by the end of the summit, Obama said that any further US compromises would only follow concrete signs from Cuba's action.

The test for all of us is not simply words, but also deeds, Obama said.