US President Barack Obama has issued a stern warning to Pakistan that it “cannot continue” to use insurgent groups to pursue policy objectives in its neighbourhood.

The warning comes in a two-page letter from Obama, which National Security Adviser James L. Jones delivered to Pakistani President Asif Ali Zardari during a meeting in November. In the letter, Obama specifically names five extremist groups: Al-Qaida, the Afghan Taliban, the Haqqani Network, Lashkar-e-Toiba, and the Pakistani Taliban organisation known as Tehrik-e-Taliban. “Using vague diplomatic language, he said that ambiguity in Pakistan's relationship with any of them could no longer be ignored,” the Washington Post reported. Obama sought closer collaboration with Pakistan against these groups. India will take heart from the naming of LeT, which it believes was responsible for the attacks in Mumbai over a year ago.

Jones, a retired Marine Corps general, was reportedly more blunt in his conversations with top Pakistani government and military leaders. If Pakistan cannot deliver, he warned, the US may be impelled to use any means at its disposal to rout insurgents based along Pakistan’s western and southern borders with Afghanistan, the Post reported. “It's going to be a game of cat-and-mouse with them for a while,” an official told the paper.

The paper said the letter from Obama also included an effort to help reduce tensions between Pakistan and India. Mindful of India's aversion for third-party mediation, Obama last week said it was “not the place of the United States to try to, from the outside, resolve all those conflicts.” The President was speaking at a joint press conference with Prime Minister Manmohan Singh.

The US is eager to reduce tensions between India and Pakistan in an effort to get the Pakistani army to focus its attention along the Afghan border. US officials believe Pakistan needs to do more. Assistant Secretary of State for South and Central Asian Affairs Robert Blake said,“I think there’s still room for further progress on that, obviously. There are still some in Pakistan who believe that India is their primary threat and not the extreme militant organisations that we spoke of.”

Obama is expected to unveil his Afghan strategy tonight at the US Military Academy at West Point, New York. While his remarks are expected to focus primarily on US commitments to Afghanistan, administration officials acknowledge that Pakistan holds the key to success. Even as Obama weighed a decision to send more US troops to Afghanistan, officials in Islamabad warned that an increased troop presence would push militants over the border into Pakistan.

British Prime Minister Gordon Brown, facing heat at home over the mounting British death toll in Afghanistan, also stepped up pressure on Pakistan over the weekend. In an interview with Sky News, Brown said, “Al-Qaida has a base in Pakistan... That base is still there-they are able to recruit from abroad. The Pakistan authorities must convince us that they are taking all the action that is necessary to deal with that threat.”