A foreign policy adviser to President Barack Obama says Republican Mitt Romney's pledge to label China a currency manipulator on his first day in office is irresponsible and risks upsetting U.S.-China relations.

At a debate Wednesday at Johns Hopkins University, Mr. Obama's former senior Asia policy aide Jeff Bader said it is “astonishing” Mr. Romney would take the step during Beijing's sensitive leadership transition, which begins two days after the November 6 election.

Bader, who serves on the president's re-election committee, said China's new Communist Party leaders will “not be in a passive mood for threats and being backed into corners.” He said he guarantees they will “retaliate.”

Romney campaign national security adviser Aaron Friedberg said the U.S. should not “be paralyzed” because of fears of sparking a trade war between the world's two largest economies. He insists the move would not “trigger Armageddon,” arguing that “China is more dependent on the United States than we are on them.”

Washington has long accused Beijing of intentionally keeping the value of its currency low in order to give Chinese companies an unfair advantage over U.S. manufacturers. But the Obama administration has refused to label Beijing a currency manipulator, instead preferring to use pressure and diplomacy to encourage reforms.

Bader says that strategy is working, pointing out that the value of the renminbi against the dollar has risen by about 30 percent since 2005. But Friedberg says the label is necessary, saying it would “put China on notice” that the U.S. is ready to act on a number of other trade violations.