MANILA, July 5 (Reuters) - Dozens of U.S.-trained commandos have joined the search for an Italian Roman Catholic priest taken captive by Muslim gunmen in the troubled southern Philippines, the country's military chief said on Thursday.

General Hermogenes Esperon said nearly 2,000 soldiers, backed by four navy boats and four helicopters, had been searching for nearly a month now in the Zamboanga peninsula to free Giancarlo Bossi, held by a rogue faction of Muslim rebels.

"We have limited our operations in a few areas in the south," Esperon told reporters.

"We're not letting up on the operations. It's just that we don't want to compromise the safety of Father Bossi."

There have been no sightings of or contacts with the priest since he was abducted after saying mass on June 10.

Kidnap-for-ransom is a thriving industry in some parts of the south, where Muslim and communist insurgents operate.

On Wednesday night, an Italian lawmaker arrived in Manila to work with Philippine officials on the case.

"Let me make it clear, I did not come here to negotiate," Margherita Boniver told reporters at the Manila international airport.

Esperon said the government has sufficient troops on the ground even after the largest Muslim rebel group, Moro Islamic Liberation Front (MILF), stopped helping soldiers search for the 57 year-old.

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