Clinton opposes new Pacific trade pact in break with Obama

Clinton, who backed the developing trade pact when she was secretary of state during Obama's first term, said she was worried the agreement would not do enough to crack down on currency manipulation or protect consumers from excessively high drug prices.

"The bar here is very high and, based on what I have seen, I don't believe the agreement has met it," Clinton said in a statement issued during a campaign swing through Iowa.

"I don’t believe we can afford to keep giving new agreements the benefit of the doubt. The risks are too high that, despite our best efforts, they will end up doing more harm than good," Clinton said.

The TPP deal, reached on October 5 after marathon talks between the United States and 11 Pacific Rim nations, aims to liberalize commerce in 40% of the world's economy and would be a legacy-defining victory for Obama.

Clinton's opposition, however, could help her shore up support from labor groups and liberal Democrats who oppose the pact out of concern it will cost manufacturing jobs and weaken environmental laws.

It is the latest in a series of moves by Clinton to distance herself from key administration policies as she tries to hold off a challenge from the left by Bernie Sanders, a US senator from Vermont, and prepare for a possible presidential run by Vice President Joe Biden.

Clinton's once-commanding lead in polls of Democratic voters has diminished amid a lingering controversy about her use of a private e-mail server when she was secretary of state, giving rise to speculation that Biden could enter the race.

Her announcement on the TPP comes just a week ahead of the first televised debate of the Democratic presidential contenders.

Obama and Biden have pushed for the trade deal, arguing it would help the United States increase influence in East Asia and counter the rise of China, which is not part of the pact.

The TPP deal, which must be approved by the US Congress, has faced skepticism from lawmakers.