American Steve Fossett was ahead of schedule as he headed towards New Zealand on Friday in his latest attempt to become the first person to fly single-handedly around the world in a balloon.

The millionaire adventurer is floating more than 6,000 metres (22,000 feet) above the Tasman Sea, and is expected to pass over New Zealand and out over the Pacific Ocean in the next few hours.

Mr Fossett, who took off from Northam, in Western Australia, could complete his flight in another 12 days, well ahead of his projected 16 to 20 days.

It is the former market trader's sixth attempt at circling the globe since 1997.

Speaking from his capsule suspended beneath his 43 metre (140 ft) tall Spirit of Freedom balloon, Mr Fossett said he was heading "straight to where I want to go".

A spokesman for his mission control team in St Louis, Missouri, in the United States said the balloonist was "on record pace so far".

Favourable weather

The greatest threat to Mr Fossett is bad weather but his team says conditions are currently favourable.

The balloon uses a mixture of helium and hot air

Although, New Zealand has been hit by severe storms over the past few days, mission control says the adverse conditions should have moved on by the time he reaches there.

His last attempt at the coveted prize, in August last year, was thwarted by bad weather.

Then he was forced to ditch in Brazil after being buffeted by high winds over the Andes, but it was still the longest recorded solo balloon flight.

Jet streams

Mission control said Mr Fossett was picking up pace in "tenacious jet streams" between a cyclone and an anti-cyclone.

They say he should reach the coast of Chile by the middle of next week, a day sooner than expected.

Once over Latin America, he is likely to be helped along by 100-knot winds, which will blow him out across the Atlantic and Indian Oceans and back towards Australia's south-west coast.

By Friday morning he had covered more than 4,000 kilometres (2,500 miles) of his 27,000 to 29,000 kilometre (17,000 to 18,000 mile) route.

Living conditions

His capsule measures 2.5 x 2.5 metres (8.2 feet x 8.2 feet) and is 1.6 metres (5.2 feet) high.

Mr Fossett is breathing oxygen through a mask and eating military-style rations.

A spate of calm weather has meant the 58-year-old has managed to get more sleep so far on this attempt than on any of his previous missions.

Mr Fossett was beaten in the attempt to be the first to circle the globe in a balloon by Swiss pilot Bertrand Piccard and English co-pilot Brian Jones in March 1999.

He then embarked on his solo quest.

In 1997, his first attempt ended in a crash landing in Russia and the following year he narrowly escaped death when a storm sent him plummeting 29,000 feet (8,800 metres) into the sea north-east of Australia.

This time many modifications have been made to plans and equipment and Mr Fossett said he was "optimistic".