The two-day "strategic economic dialogue" meeting is likely to focus on China's yuan currency, which US groups say is grossly undervalued and responsible for the widening trade gap.

A group of 21 lawmakers from the US Senate's powerful finance committee has written a letter to China's Vice-Premier Wu Yi, who arrived in Washington Monday with 15 cabinet ministers for the talks, asking her to be prepared to make "meaningful commitments" at the meeting.

Topping their list of immediate concerns is the need to "increase the flexibility of and appreciate the RMB (yuan)."

"Failure to adequately resolve these short-term issues will not only keep our long-term objectives out of reach, but also threatens to undermine the relationship between our two countries," they warned in the letter sent Friday.

Other concerns cited were China's enforcement of intellectual property rights; implementation of World Trade Organization commitments; lingering "unscientific" restrictions on US agriculture products; and tariff and non-tariff barriers on environmental goods and services.

"Progress in many areas has been long promised and is overdue," said the senators, who monitor US trade policy.

US lawmakers have accused Beijing of keeping its currency artificially low to give its exporters an unfair advantage, a key factor cited for the snowballing US trade deficit with China that hit 232 billion dollars last year.

They have also threatened to push ahead with legislation imposing sanctions on Beijing if the Chinese refused to budge.

But China's Wu Yi, known to be a tough negotiator, is unlikely to give in to their demands although she is scheduled to state Beijing's case for a stable currency as it battles various economic problems.

"Attempts to politicize trade issues should be resisted," she said ahead of her trip, accusing some US groups of overstating the US trade imbalance with China or even advocating "trade protectionism."

US Treasury Secretary Henry Paulson said in an interview Tuesday with Beijing's China Daily newspaper that progress was linked to the US presidential election set for November 2008.

"The reason I want progress so much now is that, with the presidential election coming up, I don't want people in the United States to use the lack of progress as a reason for saying, 'Dialogue doesn't work, we need tougher legislation or we need to make China an issue in the election,'" he said.

Paulson, who is leading the US side in the talks, told CNN in an interview: "Many people are looking at the fact that China is the fastest-growing global economy as a threat and what I want to do is seize an opportunity for American workers.

"We have a big focus on opening up the Chinese markets for US products and services. And that will be a big focus of our discussion today."