Politicians see China as central to the growing US trade deficit

The US Senate will vote this month on a bill to impose tariffs of up to 27.5% on some Chinese goods unless Beijing moves to free up its currency.

Some US politicians believe the yuan is artificially undervalued, letting China sell its products more cheaply abroad.

China has ruled out another revaluation after raising the yuan's value in July.

'Limited progress'

Chinese Prime Minister Wen Jiabao said recently that Beijing would allow greater flexibility in its exchange rate.

However, the Bush administration is pressing for more substantial action, believing the yuan's value is fuelling the growing US trade deficit.

Ahead of a series of meetings with senior Chinese officials, Senator Charles Schumer said the purpose of the trip was not to deliver ultimatums but to learn about Chinese intentions on the issue.

"To say that there has been no progress would be wrong but to say that there has been complete progress would be wrong," he said.

"We would like to get an idea from our Chinese hosts what the future is going to be like."