New Delhi: Prime Minister Atal Behari Vajpayee on Sunday cut short his visit to Nagpur for the Bharatiya Janata Party's (BJP's) national convention and returned to the capital on the advice of doctors.

"The prime minister has been experiencing pain in both his knee-joints for the past few days due to exacerbation of his osteo-arthritis," a statement from Vajpayee's office said.

"He had been advised rest after the Parliament session," said the statement, adding that he, however, chose to attend the national convention and the installation of Bangaru Laxman as president of the BJP.

"Since last night the pain had aggravated, causing him further discomfort. He has, therefore, on doctors' insistence, agreed to return to Delhi," the statement said.

On landing at Delhi Airport talking to the reporters Vajpayee said his trip to US scheduled to leave on September 5 is on. The PM is to participate in the Millennium Summit of the United Nations General Assembly and then pay an official visit to the United States.

In a departure from tradition, Vajpayee will board the aircraft from the international terminal of Delhi airport and not from the adjacent high-security technical area of the Indian Air Force.

From the technical area, he would have had to walk 20-odd steps up the gangway to the aircraft. From the terminal, he can get out of his car and walk into the aircraft through an aerobridge.

Shubhangi Khapre adds from Nagpur: Vajpayee suddenly left the dais while Laxman was addressing the meeting. He was immediately taken to an adjoining air-conditioned rest room. Party sources say that he complained of suffocation and uneasiness.

They said Vajpayee, who was wearing his trademark dhoti-kurta and sleeveless jacket, changed to a loose cotton kurta. He emerged on to the dais 20 minutes later and addressed the delegates while seated on the dais.

He said that he had been debating whether or not to attend the national convention. But because it was a very significant event, he had decided to attend. He also said that because of him, Home Minister L.K. Advani and Finance Minister Yashwant Sinha had also got delayed for the convention as they had all come to Nagpur together.

The prime minister had complained of uneasiness earlier in the morning too. It was later decided that Vajpayee should address the meeting and himself state that he was departing for New Delhi.

Source close to the prime minister's office said he had been feeling stressed and uneasy for some time. The heat and high humidity in Nagpur only added to the discomfiture.

"The month-long monsoon session of Parliament proved very stressful for the prime minister. Apart from the long hours in Parliament, he was also busy attending to very import national issues on Kashmir and related developments," they said.

Vajpayee was to have addressed a public meeting in Nagpur on Sunday evening. This will now be addressed by Advani.