With U.S,-Pakistan relations already shaky, a new allegation comes that intelligence officials in Pakistan may have played a support role in the worst terror attack since 9/11.
The charge comes from David Coleman Headley, a Pakistani American from Chicago who has confessed to scouting targets for the 2008 Mumbai attacks which killed more than 160 people, including six Americans.
While it's clear the attacks were carried out by the Pakistan-based terror group Lashkar e Taiba, CBS News homeland security correspondent Bob Orr reports that Headley told a court Lashkar had help from Pakistan's intelligence service, the ISI.
"They coordinated with each other," Headley testified. "ISI provided assistance to Lashkar."
That testimony came as prosecutors opened their case against a second Chicago man, Headley's former friend, Tahawwur Rana.
Rana, who ran a support service for immigrants, has denied any knowledge of the Mumbai plot.
But prosecutors say Rana was involved, and Headley has testified that Rana knew "...of his assignment to perform surveillance for potential targets in India...."
Headley is expected to return to the stand Tuesday.
The impact of the case, though, goes well beyond Rana. Headley's testimony about ISI involvement threatens to further stress U.S.-Pakistan relations at a time when "there are questions as to whether or not Pakistan was complicit in protecting Osama bin Laden for five, maybe six years, close to the heart of their capital," said CBS News national security analyst Juan Zarate.
Pakistan has denied that the ISI was behind the Mumbai attacks. But there are historical ties between the intelligence services and the terror group Lashkar-e-Taiba.
Above: Peoples' belongings are seen at the shooting site at Chattrapati Shivaji Railway station in Mumbai on November 26, 2008. A series of attacks in India's financial capital killed 164 people and wounded at least 300 more. (Indranil Mukherjee/AFP/Getty Images)