The US has offered to give West African states duty-free access to its cotton market, in a bid to inject fresh momentum into world trade talks.
The US has come under pressure to cut subsidies to cotton farmers
The offer forms part of the growing focus at the talks on measures aimed at helping the world's poorest countries.
The US and other rich states are accused of refusing to make sufficient concessions on subsidies to farmers.
Trade representatives have admitted that little progress has been made so far during the talks in Hong Kong.
Squabbling between the US and European Union over support for farmers has dominated the World Trade Organization (WTO) summit.
The World Bank waded into the agriculture argument as well, arguing that least developed countries were being treated unfairly.
"In the three days the meetings have taken so far, the rich countries have transferred more than $2bn to their farmers in various forms of support," said World Bank vice-president Danny Leipziger.
"In the same period, the 300 million poorest people in Africa have earned less than $1bn between them."
US Trade Representative Rob Portman said the US was "willing under the duty-free, quota-free commitments we will make to provide duty-free access to cotton for West African countries".
However, he signalled that the US was wary of allowing textile producers in Bangladesh full access to its market - and said concessions would only come as part of an overall trade package.
KEY TRADE FLASHPOINTS
Cotton: African cotton producers say huge US subsidies distort trade but the US says it will only agree a deal on cotton as part of wider settlement on agriculture
Bananas: EU preferences to banana producers in former Caribbean colonies were ruled illegal by the WTO and Latin American countries say tariffs are too high
Food Aid: The EU says that all food aid should be given in cash and that US grain shipments to developing countries distort the market. The US believes food aid in kind is vital in famine relief
African countries said continuing subsidies meant the concession meant little.
"They don't take in cotton, they export cotton," said Francois Traore, head of the African Cotton Producers' Association.
"What they need to do is halt the subsidies. Without subsidies they can't produce."
EU Trade Commissioner Peter Mandelson also attacked US subsidies, accusing US negotiators of "using a general smokescreen to dodge a specific commitment" to curb the annual $4bn (£2.3bn) in aid given to cotton farmers.
A failure to reach agreement on cotton was one of the issues which led to the collapse of the WTO's last conference in Cancun, Mexico, in 2003.
Meanwhile, a new clash appeared to be looming at the conference over services sector liberalisation.
Malawi suggested it might table a resolution to weaken a draft plan to open up markets for services - something that the WTO had hoped would not come up at Hong Kong.
The move is certain to be opposed by the EU, which is under pressure from EU businesses to get more concessions on services in the talks.
Earlier, developing countries urged the US and EU to offer fresh concessions on agriculture to break a logjam in the trade talks.
The G20 grouping of middle-sized economies said the EU must set a date for ending its farm export subsidies.
The US has urged the EU to go further in cutting food import tariffs, but the EU has reiterated that farming is just one factor in the negotiations.
The impasse between EU and US negotiators has prevented progress being made in other areas such as opening up trade in manufactured goods and services.