Obama's pro-trade allies battle claims that China boosts exports by manipulating its currency

Supporters of President Barack Obama's trade agenda are battling opponents' demands that China be barred from keeping its currency value artificially low.

Such "currency manipulation" can subsidize exports by making local products more affordable to foreigners.

The accusations frustrate and challenge Obama's allies on several fronts.

First, they say, it's not clear that China still manipulates its currency. And even if it does, they say the multinational trade talks underway are the wrong venues for addressing the matter.

China isn't among the 12 nations in the Trans-Pacific Partnership deal that Obama hopes to send to Congress this year.

But several lawmakers say they won't support that deal unless it includes actions on China's currency.

Some warn that crackdowns on currency manipulation might draw unwanted international attention to Federal Reserve policies.