Sen. Elizabeth Warren (D-MA) has been one of the most vocal opponents against the disastrous Trans-Pacific Partnership trade deal, currently being negotiated behind closed doors.

Yesterday, the Huffington Post asked Warren, when it comes to trade, who was the best 2016 candidate out of the current field.

“We need to hear from all our presidential contenders on trade,” Warren answered. “I will say that Hillary Clinton said in her book that she was opposed to these arbitration panels that could override domestic regulations on the environment and on workers rights and thought that they should not be part of trade deals.”

When asked about her previous comment that she wished Clinton would be clearer about her position on the TPP, Warren told HuffPo that Clinton’s “already said what she said in her book about the arbitration panels and I’d like her to weigh in on trade. I think it’s important.”

Clinton’s ambiguity on the TPP could be the reason why, when asked, Warren wouldn’t come out and endorse the former Secretary of State. Instead, Warren said that she thought it was “important for her to have a chance to lay out her views on a whole host of issues, including trade.”

Watch Sen. Warren’s interview with HuffPo.