A vote on a $1tn bipartisan infrastructure bill could be held “in a matter of days”, Senate Democratic leader Chuck Schumer said Sunday, as negotiators scrambled to finish writing the legislation.

Schumer opened a rare Sunday session by saying the text of the bill would be released “imminently”.

Senators and staff have been laboring for days to write what is certain to be a massive piece of legislation. An early draft swelled beyond 2,500 pages. To prod the work along, Schumer kept senators in over the weekend, encouraging the authors of the plan to finish drafting it so senators can begin offering amendments.

If the Senate bill passes, the House will consider the matter. On Sunday morning, one prominent House progressive fired a shot across the upper chamber’s bows.

“Bipartisan doesn’t always mean that it’s in the interests of the public good, frankly,” Alexandria Ocasio-Cortez of New York told CNN’s State of the Union. “Sometimes, there’s a lot of corporate lobbyist giveaways in some of these bills.”

A sizeable bipartisan majority in the 50-50 Senate has backed the deal in two votes, although no lawmakers have seen the final text. Votes have been on a shell bill that will incorporate the actual legislation once it is complete.

On Friday, the Senate voted 66-28 to take up the bill with 16 Republicans joining all 48 Democrats and two independents.

On Sunday morning the Republican senator Susan Collins, from Maine, told CNN she believed more than 10 of her colleagues would support the plan.

Joe Manchin, a West Virginia Democrat, said he expected the final text to be available on Sunday, allowing the Senate to proceed.

The infrastructure package is President Joe Biden’s top legislative priority.

In addition to $450bn previously approved, the package is expected to include $550bn in new spending and will dramatically ramp up expenditures on roads, bridges, transit and airports. It also includes money for scrapping lead water pipes and constructing electric vehicle charging stations.

The White House economic adviser Brian Deese talked up the bill before its final provisions were revealed, saying it would provide “badly needed investments in our economy” anf could help ease supply bottlenecks contributing to inflation.

“It will make it easier to get goods and services flowing,” Deese told Fox News Sunday. “It’ll actually lower prices over the long term.”

Pete Buttigieg, Biden’s transportation secretary, told ABC’s This Week: “Every American is going to see a difference and I think that’s one of the reasons why you had this extraordinary sight, something you just don’t see in today’s Washington very often on a major issue, which is Republicans and Democrats coming together, saying, ‘Let’s do this.’

“And for that matter, business and labor rarely are on the same page about a major economic issue, at the table saying, ‘OK, let’s get this done.’”

Supporters including Schumer and Republican leader Mitch McConnell have been optimistic about the bill’s chances – even though former president Donald Trump, still a dominant voice in the GOP, has demanded his supporters oppose it.

The bill does not include funding for climate change and social initiatives, for which progressives have pushed.

Democrats have included those measures in a separate $3.5tn package, which they will seek to pass without Republican support via budget rules. With Democratic unanimity vital, some centrist senators have wavered on whether they will support it.

Progressives have also suggested the $1tn package is inadequate and the Senate could impose changes that might complicate its chances of becoming law.

On Sunday, Ocasio-Cortez told CNN: “If there is not a reconciliation bill in the House, and if the Senate does not pass the reconciliation bill, we will uphold our end of the bargain and not pass the bipartisan bill until we get all of these investments in.

“And I want to be clear that the investments in the bipartisan bill are not all candyland … For example, some of the language around privatizing public infrastructure, putting toll roads, leasing public infrastructure to private entities, are very concerning and should be concerning to every American.

“So, we really need to see that language and see what’s put in there when it reaches the House. Bipartisan doesn’t always mean that it’s in the interests of the public good, frankly. Sometimes, there’s a lot of corporate lobbyist giveaways in some of these bills.”

Democrats’ majorities in the Senate and the House of Representatives are razor-thin, requiring the party to stick together if it wants to achieve its legislative goals.