By the BBC's Alastair Leithead in Mauritius

President George W Bush has promised to ask the US Congress to extend the lifetime of legislation granting tariff-free trade to African countries.

Mr Bush made the promise in a speech, transmitted by video link, to a forum of 38 African countries meeting in Mauritius.

The US president had originally promised to attend the conference, but cancelled his trip to Africa during the Christmas holiday, a decision many commentators have linked to the threat of war in the Middle East.

The African Growth and Opportunity Act (AGOA), which gives duty-free trade benefits, is due to expire in 2008.

'Prosperity through trade'

This has raised concerns that it would not succeed in promoting long-term investment in Africa as intended.

Mr Bush reiterated US commitment to Africa, saying: "We look to the day when prosperity for Africa is built through trade and markets."

His promise to ask for an extension of AGOA has been welcomed by businesses and African countries.

If passed, it would no doubt strengthen already-developing trade.

Whether it will go through Congress is yet to be seen.

AGOA was passed in 2000 after protracted Congressional wrangling over the extent of trade concessions, with the strongest opposition coming from Republicans.

One key focus of the AGOA conference has been to establish how to increase agricultural exports from Africa - its biggest potential trade area but one which the continent has struggled to develop because of Western subsidies.