Mullen, chairman of the Joint Chiefs of Staff, met with senior Pakistani officials as U.S. Secretary of State Condoleezza Rice met with Indian leaders to discuss the bloody assault on the Indian financial and entertainment hub last week, the Defense Department said in a news release.

The coordinated attacks killed 170 people. India blames the attacks on militants from Pakistan.

Mullen met with Pakistani civil and military leaders, including Pakistani President Asif Ali Zadari, and National Security Adviser Mahdue Durrani, the U.S. Embassy in Islamabad said.

Participants agreed that the assault in Mumbai constitutes "a dangerous escalation in the sophistication of extremist attacks that represents an increased threat to the entire region," the embassy said in a statement.

Besides urging Pakistan to explore "any and all possible links" between the assault and militant groups based in Pakistan, Mullen thanked Pakistani officials for their willingness to work with Indian authorities in a joint investigation.

Mullen also encouraged Pakistani leaders "to take more -- and more concerted -- action against militant extremists elsewhere in the country," the embassy statement said.