The Bush administration has reason to suspect a group at least partly based in Pakistan for last week's attack in India, and revealed that the U.S. had warned the Indian government beforehand that terrorists appeared to be plotting an assault on Mumbai, officials said Tuesday.

Evidence suggests that the brutal, prolonged attack on India's financial capital has some roots in Pakistan, a senior State Department official said. That's the closest the U.S. has come to placing blame for the coordinated assaults, although the official was careful to say that not all the evidence is in. The official spoke on condition of anonymity because the investigation is ongoing.

Indian authorities have claimed a Pakistan connection for days, but the United States has not wanted to "jump to conclusions," as Secretary of State Condoleezza Rice said Monday. The administration fears that any misstep amid the extraordinarily high emotions surrounding the three-day assault, which killed 172 and wounded 239 in the heart of Mumbai, could spark new and possibly deadly tensions between longtime, nuclear-armed rivals India and Pakistan.

Rice is set to visit India on Wednesday, carrying the U.S. demand that Pakistan cooperate fully in the investigation into the attacks and try to cool cross-border tempers. Among those killed in Mumbai were six Americans, White House press secretary Dana Perino said.

The revelation of a U.S. warning to Indian counterparts about a possible coming attack comes as the Indian government faces widespread accusations of security and intelligence failures in the wake of the assault.

Washington passed on information it had that a waterborne attack on Mumbai appeared in the works, said a senior administration official. This official spoke on condition of anonymity because of the sensitive nature of intelligence information. The official would not elaborate on either the timing or details of the U.S. warning.

Amid some information that the terrorists trained in camps in Pakistan, India has demanded that Islamabad hand over suspected terrorists believed living there and had said that Pakistan's leaders must take "strong action" action against those responsible.

The State Department official, traveling with Rice in Europe before her India stop, said both sides have acted "in a wise manner" so far, noting there has been no buildup of troops along the India-Pakistan border or other overt signs that sometimes sharp rhetorical exchanges will escalate to military confrontation.

On the origins of the terrorists, the official did not detail the evidence leading to a connection in Pakistan, and did not single out any one terror organization as suspect. But the official said "a variety of information, some of it public, some of it not" points to an unspecified terror group "partially or wholly ... located on Pakistan's territory."

However, the official also said that the terrorists "certainly have international reach," a fact that the administration argues demands global cooperation to combat them, including participation from Pakistan, India and the U.S.