The FBI has politely turned down India's request for extradition of terror suspect David Headley to the country on the ground that he will have to first undergo a sentence which could be imposed on him in the US for the offences committed if convicted.

Indian officials were told there was no realistic possibility of the Pakistani-American being handed over since the sentence could range between 200 and 300 years of imprisonment.

The US stand was conveyed to the Indian investigators by the Federal Bureau of Investigation (FBI) officials during their regular interaction to discuss the case related to Headley,  whose links with the banned Lashker-e-Toiba (LeT) were being probed by the two countries, official sources said in New Delhi on Sunday.

The polite turning down of the Indian request for extradition of 49-year-old Headley, arrested in Chicago on October 3, came in the wake of repeated statements including that by Union Home Secretary G K Pilai that India would press for the extradition of the terror suspect.

Pillai had said earlier that India will seek his extradition after completing investigation by January next year into his links with the Mumbai terror attacks.

However, FBI seems to be in no mood to hand over him to India and very politely conveyed that he could be handed over once the sentence ranging to 300 years is completed. He can also be sentenced to death, the sources said.

Headley has been charged by the FBI for 26/11 attacks in Mumbai also on December seven. He is alleged to have conducted reconnaissance of all targets attacked by Lashkar militants on November 26 last year besides drawing the route map for their landing on the Mumbai coast.