The top US military officer traveled to India and Pakistan on Tuesday as part of an American diplomatic effort to ease tensions over last week's Mumbai attacks.
Navy Adm. Mike Mullen, chairman of the US Joint Chiefs of Staff, was expected to arrive in the South Asia region around the same time as Secretary of State Condoleezza Rice, who was due in India on Wednesday.
Officials declined to provide further details about Admiral Mullen's trip because of the sensitivity of the situation.
The three-day rampage by 10 Islamist gunmen killed 183 people. Indian investigators say the attackers had months of commando training in Pakistan from the Lashkar-e-Taiba militant group blamed for a 2001 attack on India's parliament.
Indian warned on Tuesday that a peace process with Pakistan that began in 2004 would be at risk if Islamabad did not act decisively to turn over militant fugitives believed to be hiding in Pakistan.
US military officials worry that rising tensions could prompt Pakistan to redeploy troops to its Indian eastern border from northwestern tribal areas near the Afghanistan border where the Pakistani Army is currently operating against Islamist militant strongholds.
Admiral Mullen has met several times this year with the Pakistani army chief, General Ashfaq Kayani, to discuss the militant problem in Pakistan's Federally Administered Tribal Areas.