The gunmen who attacked Mumbai set out by boat from the Pakistani port of Karachi, then later hijacked an Indian fishing trawler that carried them toward this financial capital on their suicide mission, a top police official said Tuesday.

As evidence of the militants' links to Pakistan mounted, Mumbai police commissioner Hasan Ghafoor said ex-Pakistani army officers trained the group — some for up to 18 months — and denied reports the men had been planning to escape the city.

"It appears that it was a suicide attack," Ghafoor said, providing no other details about when the gunmen left Karachi, or when they hijacked the trawler.

The revelations came as a senior U.S. official said India received a warning from the United States that militants were plotting a waterborne assault on Mumbai. The Bush administration official, who spoke on condition of anonymity because of the sensitive nature of intelligence information, would not elaborate on the timing or details of the U.S. warning.

The Indian government is already facing intense public accusations of security and intelligence failures after suspected Muslim militants carried out the three-day attack across Mumbai last week, killing at least 171 people and wounding 239.

Indian Foreign Minister Pranab Mukherjee also said his country gave a list of about 20 people — including India's most-wanted man — to Pakistan's high commissioner to New Delhi on Monday.

India stepped up the pressure on its neighbor after interrogating the only surviving attacker, who told police that he and the other nine gunmen had trained for months in camps in Pakistan operated by the banned Pakistani militant group Lashkar-e-Taiba. On Tuesday, U.S. officials also pointed the finger at Pakistani-based groups, although they did not specifically mention Lashkar.

Secretary of State Condoleezza Rice is to arrive Wednesday, and the U.S. is pressuring Islamabad to cooperate in the investigation of the siege that paralyzed Mumbai and left six Americans dead.

Defense Secretary Robert Gates said extremists were "apparently targeting Americans and Britons, but the truth is that most of those who were attacked were Indians."

Gates also told a Pentagon news conference that the chairman of the Joint Chiefs of Staff, Adm. Mike Mullen, was headed to the region.

Of greater concern for India was the apparent failure to act on multiple warnings ahead of the Mumbai attacks, which Indian navy chief Sureesh Mehta called "a systemic failure."

India's foreign intelligence agency also had warnings as recently as September that Pakistan-based terrorists were plotting attacks on Mumbai, according to a government intelligence official familiar with the matter.

The information, intercepted from telephone conversations apparently coming out of Pakistan, indicated that hotels might be targeted but did not specify which ones, said the official, who spoke on condition of anonymity because he was not authorized to talk publicly about the details.

The information was relayed to domestic security authorities, but it was unclear whether the government acted on the intelligence.

The Taj Mahal hotel, scene of much of the bloodshed, had tightened security with metal detectors and other measures in the weeks before the attacks, after being warned of a possible threat.

But the precautions "could not have stopped what took place," Ratan Tata, chairman of the company that owns the hotel, told CNN. "They (the gunmen) didn't come through that entrance. They came from somewhere in the back."

The building was the last to be cleared, following the Oberoi hotel, the Jewish center, and other sites struck in this city of 18 million.

India said evidence from the interrogation of the surviving attacker, Ajmal Qasab, pointed to Lashkar, which was outlawed in 2002 in Pakistan under U.S. pressure.

Ghafoor said the gunmen were trained by ex-Pakistani army officers.

Qasab told police his group trained for about six months in Lashkar camps in Pakistan, learning close-combat techniques, hostage-taking, handling of explosives, satellite navigation, and high-seas survival, according to two Indian security officials familiar with the investigation. They spoke on condition of anonymity because they were not authorized to give details.

Qasab told investigators the militants hijacked an Indian vessel and killed three crew members, keeping the captain alive long enough to guide them toward Mumbai. The men then came ashore at two places, officials said.

For the first time, the U.S. also said there is reason to suspect that the terror attacks were the work of a group at least partly based in Pakistan.

The remarks, from a senior State Department official, did not detail the evidence, and did not single out any terrorist organization, but they were the closest a U.S. official has come to laying blame for the assaults.

The official, who spoke on condition of anonymity because the investigation is under way, was careful to say that the evidence was not all in.

Nevertheless, India has demanded action from Islamabad and summoned Pakistan's high commissioner to India on Monday night, giving him a list of "those persons who are settled in Pakistan and who are fugitives of Indian law," said the Indian foreign minister, Mukherjee.

India also has demanded that Pakistan take "strong action" against those responsible for the attacks.

India presented Islamabad with a similar list after the 2001 attack on India's parliament. But while tensions then between the nuclear-armed nations escalated so rapidly that many feared imminent war, the talk this time has been more subdued.

"Nobody is talking about military action," Mukherjee said Tuesday, according to the Press Trust of India news agency.

However, he later appeared to backtrack, telling the NDTV news channel that "every sovereign country has the right to protect its territorial integrity and take appropriate action."

Pakistan also seemed to be taking initial steps to comply.

Pakistani Foreign Minister Shah Mehmood Qureshi offered to establish a joint investigation with India and said the government wanted to continue a peace process begun in 2004 and broadened this year to include cooperation in fighting terrorism.

"We are examining it, we are considering it, and after consultation we will give a reply," Qureshi said of the list. "We do not want to do anything which could fan tension. We want to de-escalate matters."

He said he had told India, "We will fully cooperate with you, so that we can reach the bottom."

Topping India's list is Dawood Ibrahim, a powerful gangster and the alleged mastermind of 1993 Mumbai bombings, India's most deadly, which killed 257 people. Ibrahim fled to Dubai and later to Karachi. Pakistan has denied he is now in the country.

Several members of the list are wanted in the 1993 attacks, apparently carried out in retaliation for the demolition of a 16th century mosque by Hindu nationalists in northern India.

The other prime fugitive on the list is Masood Azhar, a suspected terrorist freed from an Indian prison in exchange for the release of hostages aboard an Indian jet hijacked to Afghanistan in 1999.

India has listed Azhar, the head of the Jaish-e-Mohammed militant group, as the "principal accused" in the attack on parliament.

India also demanded the leaders of two Kashmiri militant groups, Hezb-ul-Mujahedeen and Lashkar-e-Tayyaba, and several leaders of an uprising by Sikhs.