Sen. Elizabeth Warren of Massachusetts confronted President Donald Trump on his cherished issue of trade policy on Thursday, blistering his renegotiation of the North American Free Trade Agreement as bad for workers and a boon for large companies.

"Trump's deal won't stop the serious and ongoing harm NAFTA causes American workers. It won't stop outsourcing, it won't raise wages, and it won't create jobs. It's NAFTA 2.0," she said during a speech at American University in Washington. Barring substantial changes, she said she would vote against the deal in the Senate.

Warren's speech, billed as a rollout of her foreign policy doctrine and read carefully from a teleprompter, called for an end to the U.S. troop presence in Afghanistan, cuts to "our bloated defense budget" and a halt to the creation of more nuclear weapons. She warned of a resurgent Russia provoking the international order and a weaponized China wielding its economic might to foster oppression and attempting to leapfrog the U.S. in the technology race.

But the most defined plank in her 10-page speech centered around her most familiar turf of economics, making a play to neutralize an issue that was seen as an advantage for Trump during the 2016 campaign, as he railed against "rigged" multilateral trade deals that disadvantaged blue collar workers.

Trump is soon expected to sign a renegotiated NAFTA deal between the U.S., Mexico and Canada, rebranded as USMCA – or the United States-Mexico-Canada Agreement.

While Warren acknowledged the need to change the terms of the current NAFTA agreement, she said that Trump's revamp only has better labor standards on paper and lacks the necessary tools to enforce them.

She presented her approach as including workers in negotiating the standards and making foreign promises enforceable by empowering antitrust laws and cracking down on international tax havens.

Jonathan Tasini, a Democratic activist who authored a favorable book about Sen. Bernie Sanders of Vermont, said Warren's move into the trade debate was significant. "Elizabeth Warren has not previously been a visible leader in the movement against bad so-called 'free trade.' Staking out position now big," he said.

Warren's decision to broaden the outline of her worldview is the latest step by the Massachusetts senator toward a 2020 presidential bid.

She's been steadily working to build her foreign policy experience over the last two years from her perch as a member of the Senate Armed Services Committee. Last spring, she completed an Asia tour that included stops in China, Japan and the demilitarized zone between North and South Korea.

In June, she participated in a national security panel at the Center for a New American Security with Sen. Lindsey Graham of South Carolina, where she questioned the role of the U.S. military in solving Afghanistan's political stalemate. And she spent the 4th of July holiday visiting military personnel in Iraq and meeting with the country's prime minister.

In Thursday's speech, she specifically addressed Afghanistan, lamenting the continued U.S. presence there while calling for an unspecified "peace settlement." She also said U.S. support for the war in Yemen risks "generating even more extremism."

But despite ongoing threats, she said "Trump's nuclear arms race does not make us – or the world – any safer," proposing to extend START – the Strategic Arms Reduction Treaty – with Russia through 2026.

"We must be clear that deterrence is the sole purpose of our arsenal," she said.

Foreign policy is one area where Warren is seen to be consciously outworking Sanders , a potential 2020 rival.

Just this week, a group of 100 liberal scholars and activists criticized Sanders for including only one section in his new book about foreign policy, urging him to become more vocally opposed to militarism.

Warren, on the other hand, has been convening regular briefings with outside experts who are taking notice of her rigor in an area of perceived weakness.

Barnett Rubin, a New York University scholar who specializes on Afghanistan, was invited to Warren's office last fall to discuss the country over salad and cheap wine.

"My main takeaway was, she really engaged, she was interested, she had already learned some stuff," recalls Rubin, who hadn't met her before. "She asked really good questions and – relatively unusual in her circles – seemed genuinely interested in trying to understand the answers. She has a lot of energy."

Rubin's only experience with Sanders was during the 2016 primaries when he was dissuaded by another outside Sanders adviser from counseling him.