Top Republicans denounced Vice President Joseph R. Biden Jr. on Tuesday for saying during a visit to China that he “fully understand[s]” Beijing’s one-child policy, which has led to forced abortions and forced sterilizations.

Former Massachusetts Gov. Mitt Romney said in a statement that Mr. Biden’s words “should shock the conscience of every American.”

“Instead of condoning the policy, Vice President Biden should have condemned it in the strongest possible terms. There can be no defense of a government that engages in compulsory sterilization and forced abortions in the name of population control,” said Mr. Romney, a front-runner for the Republican presidential nomination...