This article is by Eric Schmitt, Somini Sengupta and Jane Perlez.

WASHINGTON  American and Indian authorities said Tuesday that there was now little doubt that militants inside Pakistan had directed the terrorist attacks in Mumbai. Indian officials said they had identified three or four masterminds of the deadly assault, stepping up pressure on Pakistan to act against the perpetrators of one of the worst terrorist attacks in India’s history.

The emerging consensus came as the Bush administration increased its diplomatic efforts to defuse tensions between India and Pakistan over the attacks, dispatching the chairman of the Joint Chiefs of Staff, Adm. Mike Mullen, to the region. He is to join Secretary of State Condoleezza Rice, who arrived in New Delhi on Wednesday morning.

Both officials are expected to issue stern warnings to the government of Pakistan to crack down on militant groups in Pakistan near its borders with Indian-administered Kashmir and with Afghanistan, top American aides said.

Two senior American officials said Tuesday that the United States had warned India in mid-October of possible terrorist attacks against “touristy areas frequented by Westerners” in Mumbai, but that the information was not specific. Nonetheless, the officials said, the warning echoed other general alerts this year by India’s intelligence agency, raising questions about the adequacy of India’s counterterrorism measures.

Details of the attack planners also became clearer on Tuesday. The only gunman captured by the police told his interrogators that one of the main plotters was a fugitive known to Indian authorities: Yusuf Muzammil, a leader of the Pakistani militant group Lashkar-e-Taiba, according to a senior Indian police official and a Western official.

The group, though officially banned and once focused primarily on Indian claims to disputed Kashmir, maintains its leadership in Pakistan and is believed to have moved its militant networks to Pakistan’s tribal areas.

Mr. Muzammil, who is the right-hand man to Zaki-ur-Rehman Lakvhi, the operational commander of the group, talked by satellite phone to the attackers from Pakistan when the gunmen were in the Taj and Oberoi hotels, the Western official said.

The attackers also used the cellphones of people they killed to call back to Mr. Muzammil somewhere in Pakistan, the official said.

The mounting evidence increased the pressure on the United States to find a way to resolve the tensions between Pakistan and India, two nuclear-armed neighbors. The officials said there was still no evidence that Pakistan’s government had a hand in the operation, although investigators were still searching for clues of outside support for the terrorists.

“There’s very little doubt that L.-e.-T. is responsible, but beyond that we need to learn more,” said a senior American official, who was briefed on the investigation and spoke on condition of anonymity, citing its continuing nature.

Indian officials sidestepped questions on the prospects of a military standoff and obliquely suggested that New Delhi may suspend peace talks with Pakistan, under way for nearly five years.

The Indian foreign minister, Pranab Mukherjee, said he could not comment on military options available to his government, except to say that “every sovereign country has its right to protect its territorial integrity.”

Senior Bush administration officials sought to tamp down tensions. “It’s important for there to be restraint on both sides and  but it’s also important to find out who was responsible,” Defense Secretary Robert M. Gates told reporters at the Pentagon.

Fresh information about the attacks, which hit two luxury hotels, a train station and other targets and killed 173 people, spilled forward Tuesday, even as the Indian police acknowledged that it would take longer to get to the bottom of the gunmen’s identities.

The 10 heavily armed young men had all been trained by former army officers, the Mumbai police chief, Hassan Gafoor, told reporters. Though he refused to specify, the implication was that the army officers were Pakistani.

The attackers came on a three-day journey by sea from Karachi, he said. The one suspect in custody said he was from Pakistan, and the authorities were verifying the identities of nine others who were killed.

Though the suspect in their custody has given no more than aliases for his nine partners, the Mumbai police insisted that all were Pakistanis. And all had been trained at the same place, the authorities said, and were on a suicide mission.