By Susan Cornwell

WASHINGTON (Reuters) – Senator Joe Manchin on Thursday urged fellow Democrats to pause in their push to enact a $3.5 trillion spending bill encompassing much of President Joe Biden’s domestic agenda, casting doubt on whether and when they will be able to advance the package.

“Instead of rushing to spend trillions on new government programs and additional stimulus funding, Congress should hit a strategic pause on the budget-reconciliation legislation,” Manchin, a moderate West Virginia lawmaker, wrote in an opinion piece in the Wall Street Journal.

Democrats in the House of Representatives and Senate are currently crafting legislation to fill in the details of a $3.5 trillion spending outline that both chambers approved last month.

The package, which Democratic leaders hope to pass in the coming weeks along with a $1 trillion infrastructure plan, would advance progressives’ ambitious plans to fight climate change and expand childcare, healthcare and other social programs. But Democrats need to keep the party unified to get both plans through.

“I for one, won’t support a $3.5 trillion bill, or anywhere near that level of additional spending, without greater clarity about why Congress chooses to ignore the serious effects inflation and debt have on existing government programs,” Manchin wrote in the Journal.

It was not the first time he has said the spending plan’s price tag was too high. He also did so shortly after voting to advance the $3.5 trillion budget blueprint last month, saying he was worried about the “grave consequences” of such spending on the nation’s debt as well as the country’s ability to respond to other potential crises.

Biden’s Democrats have literally no votes to spare if they are to push the spending legislation through Congress this autumn. They are seeking to advance it in the 50-50 Senate through a special budget reconciliation process that would allow it to pass with a simple majority in the chamber, where legislation usually requires 60 votes to advance. Democratic Vice President Kamala Harris holds the tie-breaking vote.

Democrats hold a razor-thin majority in the House as well, and with no Republican support expected for the $3.5 trillion plan, Manchin’s opinion – or that of any single Democratic lawmaker – matters.

Another moderate Democrat, Senator Kyrsten Sinema, has also said she will not support $3.5 trillion in spending.

Manchin’s opinion piece appeared a day after he made similar comments to the West Virginia Chamber of Commerce. Progressive (NYSE:) Democrats – many of whom have threatened not to back the $1 trillion infrastructure plan if the $3.5 trillion spending package does not pass the Senate – responded forcefully.

“Pause on finally delivering child care, paid leave, education, health care, affordable housing, climate action, and dental, vision, and hearing to millions of families across America? Absolutely not,” Representative Pramila Jayapal, chair of the Congressional Progressive Caucus, wrote on Twitter (NYSE:).