ISLAMABAD, Dec 3 (Reuters) - The chairman of the U.S. Joint Chiefs of Staff arrived in Islamabad on Wednesday as part of U.S. diplomatic efforts to defuse tensions between Pakistan and India after last week's militant attacks on Mumbai.

Admiral Mike Mullen flew in for talks with Pakistan's 8-month-old civilian government and military officials hours after U.S. Secretary of State Condoleezza Rice arrived in New Delhi for talks with the Indian leadership about the crisis.

"He'll be meeting with government officials and counterparts on regional issues," said Lou Fintor, a spokesman for the U.S. Embassy.

Rice is expected to go to Islamabad later in the week, according to officials. Mullen's visit was expected to be a short one and it was uncertain whether they would both be in Pakistan at the same time.

India has accused "elements in Pakistan" of being behind the Mumbai attacks which killed at least 171 people, including Americans and other foreigners.

The one gunman captured has told investigators he belonged to the Lashkar-e-Taiba Islamist militant group and had received training in Pakistan, according to Indian officials.

The attack has sparked fears that the two nuclear-armed neighbours could slide towards a fourth war since independence from Britain in 1947 unless cool heads prevail.

The Pakistani military has already said that it would take forces away from the Afghan border, where they have been fighting al Qaeda and the Taliban, and move them to the eastern border with India if tensions increased.

The United States and other Western governments with troops in Afghanistan will have been alarmed by the message, given by unidentified Pakistani security officials in a briefing to journalists last Saturday, that Pakistan could feel forced to abandon the U.S.-led war against terrorism to protect itself against Indian retribution. (Reporting by Simon Cameron-Moore)

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