175 people were killed in synchronized terror attacks on Mumbai targets on Nov. 26, 2008.
Since Headley and Rana were arrested in Chicago two months ago on charges that they were part of a Pakistani terrorist cell plotting future attacks in India and Denmark, the duo has been under investigation for their suspected roles in the deadly Mumbai assault.
As intelligence officers with India's National Investigation agency prepared for two days of round-table discussions with FBI agents, "They have promised us a whole lot of new material" a law enforcement source said in New Delhi.
The FBI is expected to provide Indian authorities with reports of Headley's and Rana's cellular telephone and e-mail communication with potential Mumbai attack suspects. Federal agents collected computers, records, cell phones and other evidence during raids on numerous Chicago and northern Illinois locations in October.
It was revealed last week that the FBI also conducted a five hour interview with Rana, 48, shortly after his arrest. The details of the questioning have not been made public.
Rana, a Chicago businessman and rural Illinois goat processor, is being held on terrorism charges while a federal judge determines whether he should be released on bond. The judge has asked to review the five hour interview with Rana before deciding whether he is a flight risk and a public danger. A hearing is set for mid-December in Chicago district court.
Rana's attorney Patrick Blegen said his client "categorically denies involvement in the tragic events in Mumbai of November 26, 2008. He harbors no ill will against the people of India and continues to have close family ties to the country."
Blegen, who disputes that authorities have evidence linking Rana to any terror plot, told the Ottawa Citizen newspaper "In recent years, Mr. Rana's career has been geared toward assisting members of the Hindu and other communities to become legalized and established in the United States and Canada.
"Mr. Rana has worked hard and travelled extensively to attempt to build his business. The Indian communities in Chicago, New York and Toronto are a testament to his hard work."
Headley, who ran an immigration agency and has a criminal drug history, is being held under more mysterious circumstances.
He is a Pakistan-native who changed his name from Daood Gilani and once worked as an informant for the U.S. Drug Enforcement Administration, according to police sources.
In federal custody on the Denmark/India terror plot charges since October, Headley no longer has any scheduled court appearances-having waived his immediate right to a reading of the complaint or a bond hearing. The unusual halt in public court proceedings for Headley, 49, has led to speculation that he is cooperating with federal prosecutors in the international terrorism investigation.
According to public records, published reports and law enforcement sources, Headley and Rana were reporting to Syed Abdul Rahman, a leader of the notorious Pakistani terrorist organization Lashkar-e-Taiba also known as LeT.
Rahman was allegedly the Chicago duo's go-between with Ilyas Kashmiri, a former Pakistani army commando and currently top al Qaeda general fighting US forces in Afghanistan.
During a meeting last month at the White House, President Barack Obama discussed the Headley-Rana case with India Prime Minister Manmohan Singh.
U.S. National Security Adviser James Jones said last week that Obama instructed FBI officials to share their intelligence with India regarding Headley-Rana case.