The highest-ranking US military officer on Monday encouraged Pakistan to forge "more productive ties" with India as the probe into the Mumbai attacks continues, the US embassy said here.

Admiral Mike Mullen, the Chairman of the US Joint Chiefs of Staff, was making his second visit this month to Pakistan, one of Washington's key allies in the "war on terror".

Islamabad has come under pressure from India to be more cooperative in the wake of the Mumbai attacks, which New Delhi has blamed on Pakistan-based militants. Washington has sought to calm tensions between the neighbours.

Mullen discussed the Mumbai probe with Pakistani army chief Ashfaq Kayani and Lieutenant General Ahmed Shuja Pasha, director-general of the powerful Inter-Services Intelligence (ISI) agency, the US embassy said in a statement.

"Mullen encouraged the Pakistani leaders to use this tragic event as an opportunity to forge more productive ties with India and to seek ways in which both nations can combat the common threat of extremism together," it said.

The statement said the US admiral had welcomed Islamabad's efforts to arrest members of Lashkar-e-Taiba — the group that New Delhi says was behind the deadly attacks on Mumbai, which left 163 civilians and nine gunmen dead.

"He also urged them to support judicial efforts to prosecute the cases fully and transparently," it added.

Earlier, Mullen met Pakistani national security adviser Mehmood Ali Durrani, a senior Pakistani government official told AFP.

Washington and Kabul have been heaping pressure on Pakistan to do more to combat militancy within its borders and prevent insurgents from crossing over into Afghanistan to attack US and NATO forces.

Mullen announced in the Afghan capital Kabul at the weekend that the United States could send up to 30,000 additional troops to Afghanistan by the middle of next year.

Afghan President Hamid Karzai on Monday pressed him for more details about the US plans for the troop 'surge', insisting that Kabul be consulted about where the troops are to be deployed, Karzai's office said.

Karzai has repeatedly asked that the bulk of the 70,000 troops under NATO and US command in Afghanistan be deployed in areas along the border with Pakistan.