Foreign military experts believe a 300-metre-long vessel being refurbished in the northeastern Chinese port of Dalian is destined to sail as the country's first aircraft carrier.

The Varyag, a Kuznetsov-class carrier originally built in the USSR for the Soviet navy, has had a decidedly inglorious history.

Construction began at a Ukrainian shipyard in the mid-1980s, but was interrupted by the fall of the Soviet Union in 1991.

In 1998 its immense armoured hull, with no engine, electrics or propeller, was bought at auction by a company in Hong Kong -- believed by many to have been a Chinese front -- which said it wanted to turn it into a floating casino in Macau.

Towing the Varyag from Ukraine's Black Sea coast to China proved to be an odyssey in itself.

Turkey opposed the ship's passage through its waters for months, and the vessel did not arrive in China until March 2002, after more than 600 days at sea.

The ship's military purpose soon came into focus when the People's Liberation Army (PLA) began a full refit, complete with landing platform.

"Internet source photos regularly reveal an increasing tempo of work on the Varyag," said Richard Fisher, senior fellow at the International Assessment and Strategy Center.

"The island (control tower) of the Varyag is being much modified and a new Chinese phased array radar system likely has just been installed.

"We know little about its engine but it appears that work has been proceeding on that as well. It could be moving on its own by 2011 or 2012."