The company has promised every American a free taco - if the core of Mir hits a floating target in the South Pacific.

The 144 square metre vinyl target, complete with bulls eye and the words "Free Taco here" in bold purple letters, will be anchored about 15km off the Australian coast - thousands of kilometres to the west of the expected landing area.

If Mir rings our bell, we will offer a free taco to everyone in the US

Taco Bell Corp vice president

Around 20 tonnes of the Russian orbital station's 150 tonne mass is due to fall into the sea at approximately 0630 GMT on Friday.

Fragments of Mir are being targeted at an area 200km (120 miles) wide and 6,000km long, between New Zealand and Chile.

But if Mir hits the bulls eye, the company will print free vouchers for every citizen of the United States. The whole project could cost Taco Bell about $10m.

Taco Bell is said to have taken out an insurance policy to cover the anticipated cost.

But William Ailor, director of the Aerospace Corp.'s Centre for Orbital Re-entry Debris Studies, told the Associated Press news agency the odds of Mir hitting the target were slim to none.