BOGOTÁ, Colombia — President Bush’s arrival in Colombia yesterday was marked by protests and clashes between police and demonstrators in downtown Bogotá.

Mr. Bush, the first sitting American executive to visit the Colombian capital since President Reagan in 1982, told President Uribe that America remains committed to a free-trade agreement, which has become stalled by a debate in Congress on labor and environmental standards.

“The United States is Colombia’s largest trading partner, Mr. Bush said in a joint news conference with Mr. Uribe. “It can grow even more with the free-trade agreement.”

Mr. Bush’s motorcade from the airport to Colombia’s presidential residence passed a cluster of protesters, some of whom were shouting “Get out, Bush.” In downtown Bogotá, demonstrators clashed with police, who responded to rock-throwing with tear gas canisters and blasts from water cannon.

Because of the threat of violence, Mr. Bush’s security detail was on high alert. The Colombia stop, at about six hours, is the shortest on Mr. Bush’s schedule for the five-nation trip.

Mr. Bush also is being shadowed by Venezuela’s President Chavez, who has held protest rallies and staged other events while Mr. Bush is in Latin America. Yesterday in Bolivia, he accused Mr. Bush of plotting to assassinate him, a claim he has made before and one repeatedly dismissed by the American government.

Mr. Bush has refused to engage in any sparring with Mr. Chavez, declining in news conferences to directly address questions about Mr. Chavez’s actions. Mr. Bush has focused attention on Latin American leaders who haven’t aligned themselves with Mr. Chavez, and on this trip, he has emphasized his administration’s interest in improving the lives of people in the region.

“The people of my country care deeply about the human condition,” Mr. Bush said in Bogotá. “This visit advances those values.”

America and Colombia on November 22 signed the trade accord that aimed to eliminate tariffs, deepen commercial ties, and discourage drug trafficking. Democrats in the U.S. Congress say portions may need to be renegotiated.

Mr. Bush’s visit to Colombia, the largest American aid recipient in Latin America, comes as officials there investigate alleged links between lawmakers and right-wing paramilitary fighters.