"I think it's pretty dangerous to be moving legislation through the United States Congress forcing someone to deal with the value of their currency," said House Speaker John Boehner.

He was speaking a day after the U.S. Senate voted to open debate on a bill that calls for tariffs on exports from countries with deliberately undervalued currencies. Critics of the bill have said it would stoke trade tensions just as the world economy is facing a sharp slowdown in growth.

"While I've got concerns about how the Chinese have dealt with their currency, I'm not sure this is the way to fix it," Boehner said, calling the legislation "well beyond" what he saw as the proper scope of the U.S. Congress' work.

In a possible sign of misgivings about the legislation in the White House, a top U.S. official said the Obama administration has begun discussions with the Senate about whether the bill is "the right approach" to the long-running currency issue.

Acting U.S. Commerce Secretary Rebecca Blank told CNBC television the best solution to what American officials view as an undervalued Chinese currency remains "an open question," despite signs of bipartisan support for legislation that has raised angry warnings of a potential trade war from Beijing.

"The administration is talking with people in the Senate about whether this bill is the right approach or whether there are other approaches to take," she said. "Those conversations are under way."

Senators voted 79-19 Monday to open a week of Senate debate on the Currency Exchange Rate Oversight Reform Act of 2011, which would allow the U.S. government to slap countervailing duties on products from countries found to be subsidizing their exports by undervaluing their currencies.

The latest of almost annual attacks by the U.S. Congress on a core Chinese economic policy has drawn an angry response from Beijing. China's central bank and the ministries of commerce and foreign affairs accused Washington of "politicizing" currency issues and putting the global economy at risk of a trade war.

Despite Boehner's expressed doubts about the bill, backers of the legislation in the House said the measure now has 225 co-sponsors, including 61 Republicans.

Representative Sander Levin and other Democrats at a news conference urged House Republican leaders to drop their resistance to bringing up the bill, which is expected to face a Senate vote later in the week.

Many Democrats and some Republicans accuse Beijing of deliberately holding down the value of its yuan currency to give Chinese exporters an edge in global markets.

In an argument that has gained traction with U.S. unemployment stuck above 9 percent as 2012 elections draw near, supporters of the bill say that if the yuan was allowed to rise, Chinese imports would fall and U.S. exports would increase, cutting an annual trade gap of more than $250 billion and creating jobs for American workers.