US President Donald Trump's administration supports a one-year extension of the African Growth and Opportunity Act (AGOA), the trade initiative with sub-Saharan Africa that expires on Tuesday, according to a White House official.

Since coming to office in January, the administration had not publicly stated a position on the act, known as AGOA, a law first passed in 2000 to provide duty-free access to the US market for thousands of products.

Despite broad bipartisan support for renewing AGOA, which supporters say helps diversify US supply chains and counter Chinese influence in Africa, the law's prospects for extension before it lapses are deeply uncertain.

Its only realistic legislative path is to be attached to the stopgap funding bill Republicans are pushing to keep the US government open past Tuesday, although it could also be reinstated later.

African governments and investors have been lobbying in recent weeks for a one- or two-year extension after efforts to secure a longer-term renewal did not make it to a vote in Congress.

AGOA is credited with supporting hundreds of thousands of jobs in more than 30 eligible countries.

Its impact has been diluted by the bilateral tariffs Trump introduced in August, which exposed products once exported duty-free under AGOA to US import taxes of between 10% and 30%.