Chief Judge James F Holderman has extended till January 1, 2010, the date of filing indictment for US national David Coleman Headley, arrested along with Canadian citizen of Pakistani-origin Tahawwur Hussain Rana by the FBI on charges of plotting terror attack in India at the behest of LeT.

"This court finds that the ends of justice served by extension weigh the best interest of the public and the defendant in a speedy trial because the failure to grant such an extension would deny the government the reasonable time necessary for effective preparation of the evidence for presentation to the Grand Jury, taking into account the exercise of due diligence," Judge Holderman said in his order.

Earlier, the FBI requested the court to give it more time to complete the investigation and file the indictment arguing that on October 18, federal agents executed four search warrants at four separate locations, and among other items of evidence, seized a number of computers.

The FBI agents are "diligently examining the evidence", the agency told the court.

"Additionally, further investigations regarding the full scope of the two defendant's activity is ongoing and includes gaining assistance from foreign authorities," the FBI said, without indicating which these intelligence agencies are.

Officials familiar with the probe, however, said that a team of Indian intelligence officials last week visited Washington and had a series of meetings with the FBI counterparts during which the US intelligence officials shared their investigation and interrogation details with them.

The FBI said it needed more time to complete its probe given the nature of investigation, including the time required to examine the evidence collected during execution of the search warrants and analysis and translation of the intercepted communication, coordinating with foreign authorities.