(Adds Chavez comment, Colombian reaction, paragraph 14)

By Hugh Bronstein

BOGOTA, Jan 11 (Reuters) - The release of two hostages by Colombia's Marxist rebels increases pressure on President Alvaro Uribe to meet guerrilla demands for freeing more captives, but he will likely resist.

The Revolutionary Armed Forces of Colombia, or FARC, freed two women politicians on Thursday in a deal brokered by Hugo Chavez, the left-wing president of neighboring Venezuela.

Families of some of the hundreds of other hostages hope this will lead to further breakthroughs. They want Uribe's conservative government to be more flexible in negotiating a swap of captives -- including soldiers, police and politicians -- for jailed rebels fighting a long war that kills thousands of people every year.

But Defense Minister Juan Manuel Santos said Thursday's release proves there is no need to grant the FARC's key demand for a safe-haven area where armed guerrillas could enter and turn over dozens of high-profile captives.

"This mission showed that a safe haven is not necessary," Santos told Reuters, calling on the FARC to unconditionally free the more than 700 hostages the government says are being held by the four-decade-old guerrilla army.

The impasse over a safe zone leaves dozens of "exchangeable" captives such as French-Colombian politician Ingrid Betancourt in limbo.

In a late-night televised address, an unsmiling Uribe thanked Chavez for organizing the mission but showed no sign of folding to rebel demands.

He instead solemnly read out Betancourt's name along with those of other kidnap victims still in captivity.

A FARC statement said Uribe is blocking the hostage swap that it wants to go ahead with. "We reaffirm our our disposition to work toward this objective," it said.

Uribe says to bow to the FARC's demand that he pull troops from a militarily strategic area in the southwest of the country would allow the guerrillas to regroup.

Betancourt was captured during her 2002 presidential campaign along with her running mate Clara Rojas, who was one of the two hostages freed on Thursday. The other was Consuelo Gonzalez, a former lawmaker captured in 2001.

French President Nicolas Sarkozy says Betancourt's release is a high foreign policy priority, and he has pushed both Uribe and the FARC to help win her freedom. The rebels also hold three American anti-drug contractors captured in 2003.

SECOND TRY

Uribe fell out with Chavez in November after saying the Venezuelan overstepped the bounds of his role as mediator with the rebels.

The bilateral relationship took another blow on Friday when Chavez urged the international community to stop calling the FARC a terrorist group. Colombian Interior Minister Carlos Holguin called the suggestion "off the wall."

The Venezuelan president's first attempt to win the release of Rojas, 44, and Gonzalez, 57, collapsed on New Year's Eve, in part because Uribe revealed that Rojas' 3-year-old son, who was born in a rebel camp, was in foster care and not being held by the FARC, as it had claimed.

Chavez accused Uribe of sabotaging the rescue operation and then revamped his plan, finally securing the two women's freedom on Thursday.

"The FARC did this as a political gift to Chavez, not because they have come to any agreement with the Colombian government," said a Bogota-based diplomat who asked not to be named.

"What's new is that Chavez has a direct and very public line of communication with the FARC. Meanwhile he and Uribe are not even talking," the diplomat said. "Chavez now has better relations with the Colombian insurgency than with the Colombian government. That's an ugly situation, diplomatically."

Uribe, whose father was killed in a botched FARC kidnapping in the 1980s, was reelected in 2006 after cutting crime and bolstering the economy with his U.S.-backed security push. (Editing by Kieran Murray and Eric Walsh)

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