Republican Senator Charles Grassley of Iowa is urging President Obama to declare that China is manipulating its currency, keeping the yuan value artificially low so that Chinese exports are cheap and foreign imports are expensive in the Chinese market. Obama criticized his predecessor George W. Bush for failing to say China is doing so, but has yet to make the call himself, despite two opportunities. The U.S. Treasury Department is required by law to name any country it suspects of manipulating its currency to gain an unfair trade advantage; the next report is due in April. At a meeting with Democratic lawmakers Wednesday, the president said he was concerned such currency rates could put America at a disadvantage. When G-7 finance ministers meet in Canada this weekend, they’ll discuss China’s currency policies, a Treasury official said.