Union Home Minister P Chidambaram told FBI Director Robert Mueller early this year that he suspected David Headley, who is involved in Mumbai terror attack, had not acted alone, according to a secret US embassy cable made public by Wikileaks.

At a 20-minute meeting with Mueller on February 23 during his visit to New Delhi, Chidambaram also insisted that direct access be given to Headley, even if such access produces no information, and also access to the Pakistani-American's spouse who was in Chicago, according to the February 26 cable sent by US Ambassador Timothy Roemer.

In New Delhi, Union Home Ministry sources discounted the possibility of Chidambaram having pleaded and said he may have just raised the issue of providing access to Headley for Indian investigators. The sources also noted that the veracity of the cable needed to be checked.

Mueller said Headley - who has links with the Pakistan-based terror group Lashkar-e-Taiba(LeT) - was giving the US "the best information for months" on Pakistan-based terrorist groups.

Chidambaram said he had "a feeling in my bones that Headley was not acting here(in India) alone," but conceded that he had no evidence to support his supposition that Headley formed sleeper cells in India, one of which may have been involved in the February 13 Pune bombing.

The Minister complained that Pakistan had "done damn near nothing" to prosecute Mumbai terror suspects, and Mueller said he would press the Pakistanis to take action during an upcoming visit to Islamabad, the cable said.

Chidambaram asked whether a Government of India official could monitor Headley's interrogation and submit questions "in real time," it said.

Mueller assented to Chidambaram's request for expedited FBI lab assistance regarding forensic cyber and voice recognition analysis.

Characterizing the information produced by interrogation of Headley as among the most important intelligence the US Government has gleaned in the past six to eight months, Mueller assured Chidambaram that US would continue to pass such information in a timely manner to India.

Noting that the process of Headley's proffer of evidence is nearing a critical stage, Mueller observed that Headley has expressed hatred toward India and may "clam up" if his guilty plea is tied in any way to cooperation with the Government of India.