US President Joe Biden's administration wants to work with Congress to improve a US-Africa trade pact, not just renew it without changes, US Secretary of State Antony Blinken said on Friday.

The African Growth and Opportunity Act (Agoa), a US trade initiative passed in 2000 to deepen trade ties with Africa and help African countries develop their economies, provides duty-free access to the US market and is due to expire in September 2025 after being renewed twice.

African countries are pushing for an early 10-year extension without changes to reassure businesses and investors.

"President Biden fully supports the reauthorisation of Agoa. But we don't just want to extend Agoa, we want to work with the United States Congress to make it even better," Blinken said in a video message to a US-Africa trade summit in Johannesburg, South Africa.

Despite longstanding bipartisan support for Agoa from US lawmakers, who view it as critical in countering the influence of China on the continent, there are divisions over the need for updates.

More than a dozen US senators are pushing for a quick Agoa renewal.

But the US House of Representatives, paralysed for weeks by factional fighting over its speakership, faces a daunting list of must-pass legislation.

And attempts to change Agoa risk creating an impasse similar to the one that bogged down the reauthorisation of the Generalized System of Preferences, the largest and oldest US trade preference programme, African government and US industry associations say.

South African President Cyril Ramaphosa told the Johannesburg forum that African countries wanted the US to look at the extension of Agoa for a sufficiently lengthy period to stimulate investment in new factories on the continent.

He said: "A more targeted effort to promote greater levels of investment can help to unlock Agoa's opportunities."