A Republican senator says President Barack Obama hasn't done anything about China's unfair trade practices because he needs China to keep buying the bonds that finance the growing U.S. deficit.

Speaking Wednesday at the Republican National Convention in Tampa, Sen. Rob Portman of Ohio said the United States is as beholden to China for purchasing bonds as it is to the Middle East for oil. Portman says that will end if Mitt Romney is elected president.

China holds nearly $1.2 trillion in U.S. debt.

Portman was on Romney's short-list of vice presidential candidates. He served as U.S. trade representative and White House budget director in George W. Bush's administration.

Romney has accused China of manipulating its currency and blocking access to its markets.