China's leader-in-waiting Xi Jinping on Wednesday confronted US lawmakers skeptical about Beijing's pledges to improve its rights record, ease its grip on the yuan and boost military cooperation.

Xi, the vice president expected to assume the mantle of power next year in Beijing, made the rounds on Capitol Hill in an election year which has seen President Barack Obama's Republican foes accuse him of being soft on China.

The Chinese heir apparent's foray into the seat of US politics comes amid flaring suspicion of China on both sides of the aisle, fanned in part by a hesitant US economic recovery.

Senate Majority Leader Harry Reid smiled and shook hands with Xi at the start of a meeting with top senators, but there were none of the usual pleasantries before journalists were ushered out of the room.

Xi, who is expected to succeed Chinese President Hu Jintao in 2013, later crossed the Capitol to meet with Republican House Speaker John Boehner and other leaders.

The US list of concerns is crowded: from unfair trade practices, the allegedly undervalued yuan, industrial espionage and forced technology transfers to China's rapid military modernization, treatment of dissidents and stances on crises like Syria.

Republican Representative Ileana Ros-Lehtinen, chair of the House Foreign Relations Committee, used Xi's visit to accuse Obama of "one dangerous concession after another" to China.

"Responsible nations must be committed to confronting the Chinese regime on its dark human rights record," she said, specifically demanding the release of human rights lawyer Gao Zhisheng, who has hardly been heard from since 2009.

"I also urge the administration not to cave to Chinese demands concerning US strategic alliances and military presence in the region," Ros-Lehtinen said.

But in a speech to business leaders after his meetings on Capitol Hill, Xi set aside the tensions and stressed that relations between the two powers were an "unstoppable river that keeps surging ahead" despite twists and turns.

"It is a course that cannot be stopped or reversed," he said, describing the ever more intertwined interests of the world's top two economies.

"Chinese-US relations are now at a new historical starting point in the second decade of the 21st century."

At the White House on Tuesday, Obama told Xi the United States wanted to make sure "everybody is working by the same rules of the road when it comes to the world economic system."

"That includes ensuring that there is a balanced trading flow not only between the United States and China but around the world," Obama said.

The US press in recent days has highlighted dramatic cases of alleged cyberespionage originating from China and targeting Western industries.

The New York Times reported Wednesday that Senator John Kerry intended to raise with the Chinese the case of a Massachusetts wind energy company, American Superconductor Corporation, whose Chinese partner allegedly stole key technology.

The Wall Street Journal this week disclosed that hackers believed to be based in China penetrated a now bankrupt Canadian telecommunications company, Nortel, and had access to its entire system for at least a decade.

Political sentiment has risen so high in Congress that the Senate last October passed a measure threatening retaliatory duties against China for allegedly manipulating its currency, infuriating Beijing.

Boehner stepped in and blocked the measure in the House, citing the risk of a "trade war" if it passed, a reflection of the countervailing view that US and Chinese economic interests are too intricately intertwined to jeopardize.

In the last decade trade between the two countries has increased over 275 percent and is now worth half a trillion dollars a year.

But Republican presidential candidates like Mitt Romney have been unsparing in their attacks on China, raising the temperature in relations.

China's recent veto of a UN resolution condemning the violence in Syria, and its reluctance to support sanctions against Iran, a major oil supplier to Beijing, also have added to the tensions.

Vice Foreign Minister Cui Tiankai, who is accompanying Xi on his US visit, told reporters late Tuesday "all people are calling for an immediate end to the bloodshed in Syria. Yet if the Security Council takes one wrong step, it is likely to lead to more bloodshed instead of putting a stop to the bloodshed."

After his immersion in Washington politics, Xi heads later Wednesday to friendlier ground in Iowa. The midwestern farming state counts on China as a rapidly growing market for its pork, soybeans and other produce.