Dozen die in Mexico clash ahead of Obama trip: media

The soldiers were patrolling a remote mountain road in the southern state of Guerrero on Wednesday when they ran into heavily armed drug gangsters who opened fire on them, Reforma newspaper said. The soldiers returned fire.

Obama was to arrive in Mexico City on Thursday for his first visit to Latin America and Mexico's escalating drug war will top the agenda.

Some 6,300 people died last year in drug killings in Mexico and the violence has begun to spill over into the United States.

The Obama administration is tightening the U.S.-Mexico border to prevent trafficking of U.S. guns to Mexican cartels and is hoping to send Black Hawk helicopters to help Mexican President Felipe Calderon defeat well-armed cartels.

Reforma said 13 people, including a soldier, died in the shootout in Guerrero. Another daily, El Universal, said the traffickers threw grenades at the soldiers and at least 10 people were killed. The traffickers were bringing drugs down from the mountains, El Universal said.

The region is known for its crops of marijuana and poppy, which is used to make heroin.

Mexican officials want Washington to reinstate a ban on assault weapons that expired in 2004. Some 90 percent of weapons used by Mexican gangs like the Gulf and Sinaloa cartels come from the United States, Mexican police say.