The Ministry of Foreign Affairs and the Ministry of National Defence did not respond to requests for confirmation yesterday.

The Nimitz, a nuclear-powered aircraft carrier and one of the world's largest warships, is at present in port in Kuala Lumpur, Malaysia, on routine deployment in the region. The Nimitz completed a mission to support coalition troops in Afghanistan on January 25.

The Hong Kong visit has surprised many military observers who believed Beijing's approval would have been impossible given the bilateral tensions triggered by two rounds of US arms sales to Taiwan.

Beijing retaliated over the sales by suspending planned military exchanges and, for the first time, vowing to impose sanctions on US firms involved in the arms sales. The Defence Ministry said in a strongly worded statement on January 30, a few days after the second arms sale, that Beijing had 'decided to suspend planned mutual military visits'.

To add to Sino-US tensions after a honeymoon period last year, the White House says US President Barack Obama plans to meet the Dalai Lama, despite repeated protests from Beijing.

The Nobel Peace Prize laureate and exiled Tibetan leader, denounced as a separatist by Beijing, will be in Washington on February 17 and 18, according to the Dalai Lama's office. The White House has yet to announce when and where the meeting will be held.

Hong Kong-based military attaches said they would watch the USS Nimitz visit closely to see whether Beijing sent People's Liberation Army officers to functions on board.

Typically US naval brass host parties aboard during port calls in honour of their host nation as a way to boost informal ties.

'Technically a routine ship visit is not really a military exchange ... but all the rest of the activities surrounding it could be seen that way,' one Asian military attache said. 'It will be a good way of detecting how serious China is really pushing this.'

But the coincidence of the timing of the fleet's arrival in Hong Kong and the Dalai Lama's visit to Washington led many military observers to doubt whether the port call would go ahead.

In 2007, the aircraft carrier USS Kitty Hawk was denied entry to Hong Kong on a port visit coinciding with the Thanksgiving Day holiday in the US. Observers linked the denial to US president George W. Bush's presentation of a congressional medal to the Dalai Lama in Washington. The aircraft carrier and its battle group was on course for Hong Kong but had to return to its home port Japan after Hong Kong officials said they had not received Beijing's approval for the visit. Beijing said later that it could dock but the fleet was en route for Japan by then.

Xu Guangyu, a retired PLA major general, said it was unlikely that Beijing would have approved the latest port call unless compromises had been made.

'It's either that Obama has agreed not to meet the Dalai Lama or the two countries have made some under-the-table agreements to back off from sensitive issues, otherwise I don't think it was possible that the port call could have happened,' Xu said. 'Or Beijing may want to use the port call to send out a signal to Washington that Obama should not meet the Dalai Lama in a too high-profile manner.'

Anthony Wong Dong, president of the International Military Association in Macau, said that although the port call was unlikely, Beijing could be using it as a way to mend broken military ties.

'The US side is definitely using the port call request to test the waters,' Wong said. 'It's very unlikely that the port visit will happen and you will have to wait until the last minute to see if it really happens. If it really happens, maybe it's because Beijing wants a subtle way to get them both out of the military predicament.'

Additional reporting by Greg Torode