Richard Norton-Taylor and Luke Harding: Go now, Britons told as Kashmir war looms

Britain and the US urged their nationals to leave India and Pakistan yesterday as fear of a nuclear war over the disputed state of Kashmir grew.

The foreign secretary, Jack Straw, issued the upgraded British warning after Pakistan played down a call from India for joint patrols along the ceasefire line of control which divides the Indian and Pakistani controlled sections of Kashmir.

Last week Mr Straw told Britons to "consider" leaving: yesterday he changed the advice to "should" leave.

"It remains my view that war between India and Pakistan is not inevitable, and with our international partners we continue to do all we can to avert a crisis," his statement said.

"However, given ... the continuing tensions between the two countries, I have decided to make this further change to our travel advice."

The US state department warned Americans to leave, saying that the tension had "risen to serious levels".

The new advice followed an increase in military exchanges in Kashmir, the Foreign Office said. Intelligence assessments seen by ministers said there was a real risk of nuclear war.

The US defence secretary, Donald Rumsfeld, stepped up the international pressure on India and Pakistan after talks in London with Tony Blair and Geoff Hoon, the British defence secretary.

Mr Rumsfeld, who is travelling to India and Pakistan next week, said: "These are not just larger weapons; they are distinctively different weapons, and war being what it can be, it can be unpredictable".

But he made it clear that the US did not intend to act as a mediator in the crisis.

President George Bush telephoned the Indian prime minister, Atal Bihari Vajpayee, and Pakistan's military leader, General Pervez Musharraf, to urge them to reduce the tension in the region, the White House spokesman, Ari Fleischer, said.

"The president reiterated to President Musharraf that the US expects Pakistan to live up to the commitment Pakistan made to end all support for terrorism," Mr Fleischer said.

"The president emphasised to Prime Minister Vajpayee the need for India to respond with de-escalatory steps."

Mr Vajpayee tried to regain the diplomatic upper-hand yesterday by proposing that forces from both sides should jointly patrol their disputed border.

He said India and Pakistan should work together to verify that Islamist militants were no longer crossing into Indian-ruled territory.

"Pakistan claims that they have controlled infiltration" he said.

"We want to test the ground. Once the terrorist camps are destroyed and infiltration stops and we have proof of this, we can then start taking other steps to reduce tension.

"We want to move away from a path of confrontation to a path of cooperation."

The offer was made at the end of an acrimonious regional security summit in Kazakhstan. It came after Mr Vajpayee rebuffed several attempts by the Russian president, Vladimir Putin, to set up a meeting between him and Gen Musharraf. Last night Pakistan's foreign ministry dismissed Mr Vajpyaee's overture as "not new".

"Given the state of Pakistan-India relations, mechanisms for joint patrolling are unlikely to work," it added.

Earlier, Gen Musharraf said that India "should not be the accuser and the judge" of movement on the line of control. He suggested monitoring by the US or UN.

India, on the other hand, insists that Kashmir is a problem between their two coun tries. Mr Vajpayee dismissed the call for foreign observers as neither "practical" nor "advisable".

India accuses Pakistan of allowing Islamist militants to infiltrate Indian Kashmir and attack Indian security forces. Gen Musharraf claims that infiltration has stopped, and has given private assurances to London and Washington.

Mr Vajpayee said yesterday that there had been joint patrols in the past. But there is no history of cooperation along the the 460-mile long cease-fire line where India and Pakistani forces fought each other to a halt during their first war over Kashmir, in 1947-8.

A handful of UN observers already monitors the frontline, and Pakistan said last night that it would like to see their number increase. Since January about a million men have been dug in at the border.

Pakistani officials said two civilians were killed by overnight Indian shelling.

India, for its part, said its security forces shot dead six people in the town of Poonch and claimed that they were members of a Pakistani-based militant group, Lashkar-e-Toiba.

Mr Vajpayee told a news conference in Almaty that 3,000 Islamist militants were being trained in Pakistan.