Armed with many documents, which prove the ISI's links with terror groups like Lashkar-e-Taiba, India may implead itself in the lawsuit filed in the federal court to help the petitioners as well as declaring ISI as a terrorist outfit.

"Our main purpose is to help the family of the Rabbi to get justice as well as to prove in the New York court ISI's direct link with terror outfits like LeT which carried out the Mumbai attack," a government official said.

If the New York court is convinced about ISI's role in 26/11 attack, it will strengthen the case of declaring ISI as terrorist outfit by the US and the UN.

In the lawsuit, ISI chief Shuja Pasha and LeT are being sued for the Mumbai attack. It was filed by the close family members of Rabbi Holtzberg and Rivka, who were killed by the terrorists at the Chabad House in Mumbai during the 26/11 attack.

The disclosure of LeT operative David Headley in a Chicago court that he was in constant contact with ISI officials and he received espionage training from ISI is also likely to strengthen the lawsuit.

Headley's testimony in the trial of Pakistani-Canadian Tahawwur Rana in a Chicago court that the Pakistani spy agency and its operatives like Major Iqbal and LeT founder Hafiz Saeed had helped him in laying the groundwork for the Mumbai attacks has exposed Islamabad's role in 26/11, the government official said.

Through records of several emails exhibited in the court, federal prosecutors established beyond doubt that Headley was in constant contact with ISI officials, in particular Major Iqbal, and his handlers in Pakistan.

In one of the emails to his ISI handler Major Iqbal, Headley writes about the latest spying gadgets.

Headley told the court that Iqbal made key decisions and was indeed the mastermind of the 26/11 plot.

"Major Iqbal told me the Chabad House would be added on whatever list (of targets) there was because it was a front office for the Mossad" - Israel's intelligence agency, Headley said, adding that Major Iqbal "seemed upset the (Mumbai) airport was not included" as a target.

"If we become party to the law suit, all these will come as great help in proving our point that ISI is nothing but a global terrorist organisation," the official said.