The United States opened annual trade talks with African nations in Zambia's capital Lusaka on Thursday, looking at ways to diversify the continent's exports under an 11-year-old preferential trade deal.

Thirty-seven African nations qualify for duty-free access to the US market under the African Growth Opportunities Act (AGOA), which requires beneficiaries to meet standards for free-market economies and good governance.

The ministerial meeting in Zambia will look at ways to encourage African nations to diversify their exports to include more manufactured and value-added products.

"AGOA is changing the lives of millions of people in Africa and President (Barack) Obama's administration is committed to make AGOA work much better," US Trade Representative Ron Kirk said at the opening.

The host of the meeting, Zambian President Rupiah Banda, urged more countries to adhere to democratic principles to reap the benefits from the trade deal.

"Some African countries are not represented here today because of ongoing social political instability," Banda said.

"This reality reminds us that the economic dividends we seek from AGOA can be best realized when all African countries strengthen and enrich sound democratic practices and uphold good governance," he said.

"Peace and security within and across borders are twin imperatives that all must not fail to work for," Banda told the delegates.

Last year AGOA exports to the United States reached $44 billion, but 91 percent of that was petroleum products, mainly from Nigeria and Angola, according to the State Department.

Most manufactured goods sold to the United States under AGOA come from regional powerhouse South Africa, with the rest of the continent sharing the small remainder.

About 1,600 delegates from 31 nations are attending the two-day meeting to look at ways to boost exports of apparel, footwear, processed agricultural goods, and other manufactured products.

US Secretary of State Hillary Clinton is due to join the meeting for its closing session on Friday.