The FBI is sending a team to Pakistan and India as part of an inquiry into a Chicago man accused of plotting against a Danish newspaper and sizing up targets ahead of last year's deadly terrorist attacks in Mumbai, India's financial capital.

Pakistan's role in alleged plots spanning three countries has increasingly come under scrutiny as new details emerge about the case and suspect David Coleman Headley's links to the country.

Headley, 49, an American of Pakistani descent, and Chicago businessman Tahawwur Rana, 48, a Pakistani-born Canadian national, were charged in October with conspiring to attack the Jyllands Posten newspaper in Denmark. The newspaper had published 12 cartoons depicting the Prophet Muhammad in 2005 that set off protests in parts of the Muslim world.

The U.S. charges also said Headley, who had changed his name from Daood Gilani, had attended militant training camps in Pakistan and conspired with members of the Pakistan-based militant group Lashkar-e-Taiba to conduct extensive surveillance on potential targets in the Indian city of Mumbai before the terrorist attacks there in November 2008 that left 166 people dead.

The U.S. allegations offer a vivid illustration of Pakistan's militant problem as the Washington presses Islamabad to do more to stop it from spilling over the border into Afghanistan.

Headley was born in Washington as Daood Gilani to a Pakistani father and American mother who later moved to Pakistan where he spent his early years.

He met Rana when they were both teenagers at the Hasan Abdal Cadet College, a prestigious Pakistani boarding school with red brick buildings and manicured grounds outside the capital, Islamabad.

They both entered in 1974, but only Rana completed the five-year term. Administrators say Headley left after three years to go live with his mother, who had returned to the United States after divorcing his father. The two maintained contact with graduates of the academy via e-mail as part of an alumni group.

Headley's half-brother, Danyal Gilani, said the family had little contact with Headley after he left for the U.S.

The half-brother, who is a public relations officer for the prime minister, said he last saw Headley when he visited Pakistan a few days after their father died last December.

The U.S. charges indicate Headley apparently was in Pakistan as late as January to contact Ilyas Kashmiri, who has been linked to al-Qaida and described as a leader of the terrorist group Harakat-ul Jihad Islami.

Headley could be sentenced to death if convicted on the charges involving the terrorist attacks in Mumbai. Headley's attorney, John T. Theis, said he would "continue to look at this and see what the evidence is," but declined to comment further.

A retired major in the Pakistani military identified as Abdur Rehman Hashim Syed also was charged Monday with conspiring to attack the Danish newspaper and its employees, according to U.S. court documents. Pakistan has said it has a retired major in custody for questioning over alleged links with Headley and Rana, but officials Tuesday gave no details about where he was being held or what charges he might face.

The country's security agencies have a long history of supporting Lashkar-e-Taiba and other militant groups as proxies against arch-rival India in the disputed region of Kashmir. Islamabad says it no longer backs such groups, but many powerful Pakistani politicians and army officers are believed to remain sympathetic to the cause, raising concerns they could be potential recruits for more global Islamist extremists like al-Qaida.

The FBI team arrived in India on Monday.

"Both our countries are working closely together to share information on the Headley-Rana case and working to detect and prevent future threats," the U.S. Ambassador to India, Timothy J. Roemer said in a statement.

U.S. Embassy spokesman Rick Snelsire said the FBI team also will brief security officials in Pakistan and are working with them to follow leads on Headley's activities in Pakistan.

India, which has long blamed Lashkar-e-Taiba for the Mumbai rampage, welcomed the charges.

"Obviously the FBI must be having substantial evidence to back the arraignment of Headley. We do hope that the United States would bring pressure to bear on Pakistan to have uniform standards on controlling terrorism on both their eastern and western borders," Manish Tewari, spokesman of India's ruling Congress party, said Tuesday.

A two-count complaint against the retired Pakistani major was filed under seal Oct. 20. It says he coordinated surveillance of the Danish newspaper and participated in planning the attack there along with Lashkar-e-Taiba and Kashmiri — described as a leader of the terrorist group Harakat-ul Jihad Islami.

Authorities say Abdur Rehman took Headley in January to terrorist safe havens near the western Afghan border. The aim was to solicit Kashmiri's help in launching the attack against the Danish paper, the charges say. A search of Headley's luggage at the time of his arrest turned up a list of phone numbers including one allegedly used to contact Abdur Rehman.

Riffat Hussain, a professor of Defense Studies at Quaid-e-Azam University in Islamabad, said militants networks were becoming increasingly intertwined and recruiting from regional groups such as Lashkar-e-Taiba.

Pakistan's Inter-Services Intelligence agency severed its links to the groups after the 2001 terrorist attacks in the United States but many past members have formed alliances with al-Qaida and other insurgent groups that attack the United States in Afghanistan and other Western targets, analysts say.

Al-Qaida and other Islamist extremist groups "would like to draw upon these old jihadi elements and use them essentially as an instrument," Hussain said.