Mexican troops cross U.S. border, hold agent

PHOENIX (Reuters) - Mexican soldiers briefly held a U.S. Border Patrol agent at gunpoint in a remote stretch of the Arizona desert after they mistakenly strayed north across the border, authorities said on Wednesday.

Tucson sector Border Patrol spokesman Mike Scioli said four Mexican soldiers wearing desert camouflage and carrying weapons confronted the agent early on Sunday morning as he patrolled a border road in the Tohono O'Odham nation southwest of Tucson.

Scioli said the agent repeatedly identified himself in English and Spanish. After four minutes the soldiers lowered their weapons and crossed back in to Mexico on foot.

The stretch of desert is frequently crossed by human and drug smugglers from Mexico, and the border line in the area is not always clearly marked, Scioli said.

A spokesman for the U.S. State Department said the incursion had been brought to the attention of the Mexican government, and appeared to be accidental.

"Our understanding is that this encounter stemmed from a momentary misunderstanding as to the exact location of the U.S.-Mexican border," Gonzalo Gallegos said.

"We recognize that occasional incidents such as this can and do occur. But we take the misunderstanding seriously, as does the Government of Mexico."

Incursions by Mexican military personnel into the United States over the nearly 2,000-mile (3,200-km) southwest border are not uncommon. Scioli said 42 incidents had been reported since October 1 last year.

(Reporting by Tim Gaynor; editing by Alan Elsner)