For the first time, India has turned over to Pakistan what it says is written proof that the sole surviving suspect from the Mumbai terror attacks is a Pakistani citizen.
The attacks killed more than 170 people and paralyzed India's richest city for three days.
A letter written by the sole surviving gunman, Mohammad Ajmal Ameer Qasab, was delivered to the acting high commissioner in New Delhi this evening. According to India's foreign ministry, Qasab "stated that he and the other terrorists killed in the attack were from Pakistan." Pakistan's foreign ministry acknowledged that only Qasab "claims to be a Pakistani."
Pakistan received the letter about the same time that the chairman of the Joint Chiefs of Staff, Adm. Mike Mullen, arrived in Islamabad. It was his second visit since the Mumbai attacks, part of an effort to defuse tensions between Pakistan and India.
Indian authorities long ago identified Qasab as one of the 10 gunmen who stormed Mumbai Nov. 26. Qasab was captured after he opened fire in the city's main train station, killing dozens.
Pakistani authorities continue to try to distance themselves from the attacks. Late last week, President Asif Ali Zardari rejected media reports that Qasab used to live in the small Punjab city of Faridkot, saying only that "the investigation is ongoing."
But in interviews with Western and Pakistani newspapers, residents of the village have said Qasab's family was quickly moved out of the village after the attacks. And Qasab's father told the Dawn newspaper, "This is the truth. I have seen the picture in the newspaper. This is my son Ajmal."
Pakistan has increasingly become to doubt Indian intentions in the last few days, leading the military to take steps to defend itself in case of an Indian attack.
Tension between India and Pakistan, a senior Pakistani military official told ABC News, is increasing by the day. On a scale of 1 to10, the tension is at a 7, the official said.
Pakistan has reinforced its positions on the border since the Mumbai attacks, and the official said last night it had reinforced them further by redeploying troops.
There had been some movement of troops from the troubled region of Swat, where the military has fought the Taliban and allied groups, to the eastern border with India, the military acknowledged.
And the military recently canceled the movement of some troops from the Punjab to the North West Frontier province, a Pakistani official said.
The air force is on high alert, and pilots are in their combat gear 24-7, the official said.
This is less about Indian moves, which have not included any serious redeployment of troops, than a lack of trust.
"We can't trust them," one military official said, and so the Pakistani military is taking "no chances."
India and the United States both said Lahskar-e-Taibi, created with the help of Pakistan's intelligence services 20 years ago, was behind the Mumbai attacks.
Both countries have put pressure on Pakistan to crack down on the group, as well as the charity Jamaat-ud-Dawa, which the Security Council two weeks ago labeled a front for Lashkar-e-Taiba.
The U.S. pressure on Pakistan spiked over the weekend, when Secretary of State Condoleezza Rice met with Pakistan's national security adviser, Madmud Ali Durrani.