Democratic Arizona Sen. Kyrsten Sinema announced Wednesday that she will not support the $3.5 trillion infrastructure package that her party’s leadership hopes to pass via reconciliation.

“I do not support a bill that costs $3.5 trillion—and in the coming months, I will work in good faith to develop this legislation with my colleagues and the administration to strengthen Arizona’s economy and help Arizona’s everyday families get ahead,” she told The Arizona Republic. Sinema added that she will vote to begin debate on the reconciliation package.

The announcement is a major setback for the furthest-left members of the Democratic Party, who have frequently criticized Sinema for her efforts to forge a bipartisan bill on infrastructure and support for the filibuster. Sinema met Tuesday with President Joe Biden to discuss the bipartisan infrastructure deal, describing their discussion as “productive.”Sinema has worked alongside Republican Sens. Mitt Romney of Utah and Rob Portman of Ohio on the infrastructure agreement.

Biden announced in June that he will only support the bipartisan agreement “in tandem” with a reconciliation package. That approach has been endorsed by prominent left-wing Democrats, including Speaker of the House Nancy Pelosi, Senate Majority Leader Chuck Schumer, Massachusetts Sen. Elizabeth Warren, and Tlaib’s fellow ‘Squad’ member Minnesota Rep. Ilhan Omar.