By Susan Cornwell

WASHINGTON, April 9 (Reuters) - President Barack Obama should insist that Cuba release all political detainees before the United States moves to relax trade and travel restrictions with that country, two U.S. lawmakers said on Thursday.

With Obama and Congress reviewing the decades-old U.S. policy of isolating communist Cuba, the Republican lawmakers urged them not to forget human rights on the island 90 miles (145 km) from U.S. shores.

Representatives Frank Wolf and Chris Smith criticized some of their fellow lawmakers who made a recent visit to Cuba, saying they failed to publicly focus on human rights.

Wolf and Smith, both members of the Congressional Human Rights Caucus, urged Obama to read a 2008 State Department report that said Cuba had at least 205 political prisoners. It also said that as many 5,000 Cuban citizens were detained for "dangerousness," but had not been charged with any crime.

"This administration ought to be very careful. They ought not to lift sanctions until the prisoners are out," Wolf told a news conference.

Obama's staff has said he will announce shortly a lifting of restrictions on family travel and remittances between the U.S. and Cuba. In Congress, there is growing bipartisan support for reforming the U.S. policy of isolating Havana, which began soon after Fidel Castro took power in 1959.

The president is preparing for an April 17 Summit of the Americas in which Latin American leaders are expected to press for an end to the U.S. embargo on the island, which has been in place since 1962.

But Obama has said he will maintain the embargo until Cuba shows progress on human rights and democracy. And while some U.S. lawmakers would like to see trade restrictions eased, others from districts with numerous Cuban exiles strongly oppose change.

Fidel Castro on Wednesday hailed as "magnificent" the recent talks in Havana with several members of the Congressional Black Caucus. They met him as well as his younger brother President Raul Castro, who became president last year.

But Smith and Wolf accused the group of "gushing" with praise for the Cuban government while minimizing human rights.

"Sadly, to the best of my knowledge, they did nothing publicly to show any concern for the myriad gross human rights abuses perpetrated by the Cuban government," Smith said.

He and Wolf said talks with Cuba's government are fine so long as human rights are "front and center". They are seeking visas to visit Cuba to visit political detainees, and they are open to the idea of naming a special U.S. envoy to the island.

Such an envoy has been suggested by Indiana's Senator Richard Lugar, a leading Senate voice on foreign affairs. Lugar has also suggested that at the Summit of the Americas Obama should drop U.S. opposition to a discussion of allowing Cuba to join the Organization of American States. (Editing by Anthony Boadle)