Sen. Susan Collins, R-Maine, center, and other Senate Republicans negotiating a $1 trillion infrastructure bill with Democrats announce they have reached agreement on the major outstanding issues and are ready to vote to take up the bill, at the Capitol in Washington, Wednesday, July 28, 2021. Credit: J. Scott Applewhite / AP

WASHINGTON — The Senate voted Wednesday night to begin work on a nearly $1 trillion national infrastructure plan after President Joe Biden and a bipartisan group of senators reached agreement on major provisions of the package that is a key part of his agenda.

Biden welcomed the accord as one that would show America can “do big things” with the most significant long-term investments in nearly a century, he said, on par with building the transcontinental railroad or the interstate highway system.

The rare bipartisan showing, on 67-32 vote, signaled the interest among senators in starting the process to consider the infrastructure package. But it’s unclear if enough Republicans will eventually join Democrats to support its final passage. The procedural step Wednesday night is expected to launch lengthy consideration.

“Our bill has an historic investment, not only in roads and bridges and airports and seaports and waterways and the electric grid, but also in broadband, and I’m very proud of what all of us have done,” said Sen. Susan Collins, R-Maine, who was among the lead negotiators in her party, at a press conference after the Wednesday night vote. “We’ve still got a long way to go before we get to the finish line, but this was a vitally important first step.”

That group worked with the White House to salvage the deal, a first part of Biden’s big infrastructure agenda. Swelling to more than 700 pages, the bill includes $550 billion in new spending for public works projects.

In all, 17 Republican senators joined the Democrats on Wednesday in voting to launch the debate, but most remained skeptical. The GOP senators were given a thick binder of briefing materials during a private lunch, but they asked many questions and wanted more details.

The five-year spending package would be paid for by tapping $205 billion in unspent COVID-19 relief aid and $53 billion in unemployment insurance aid some states have halted, according to a 57-page GOP summary obtained by The Associated Press. It also relies on economic growth to bring in $56 billion among other items.

The outcome will set the stage for the next debate over Biden’s much more ambitious $3.5 trillion spending package, a strictly partisan pursuit of far-reaching programs and services including child care, tax breaks and health care that touch almost every corner of American life. Republicans strongly oppose that bill, and may try to stop both.

Senate Majority Leader Chuck Schumer, D-New York, opened the Senate announcing a possible evening vote, nudging talks along. It takes 60 votes in the evenly split 50-50 Senate to proceed for consideration and ultimately pass the bill, requiring support from both parties.

Giving that a boost, Senate GOP leader Mitch McConnell announced late Wednesday he would vote to proceed, though whether he will support the final bill remains uncertain. The Republican negotiators met with McConnell earlier Wednesday and Portman said the leader “all along has been encouraging our efforts.”

Sen. Kyrsten Sinema of Arizona, a lead Democratic negotiator who talks often with Republicans, said she also spoke with Biden Wednesday and he was “very excited” to have an agreement. Democrats, who have slim control of the House and Senate, face a timeline to act on what would be some of the most substantial pieces of legislation in years.

Filling in the details has become a month-long exercise ever since a bipartisan group of senators struck an agreement with Biden in June over the broad framework. The new spending in the package dropped from about $600 billion to $550 billion, senators said, as money was eliminated for a public-private infrastructure bank and was reduced in other categories.

The package still includes $110 billion for highways, $65 billion for broadband and $73 billion to modernize the nation’s electric grid, according to a White House fact sheet. There is $25 billion for airports, $55 billion for waterworks and more than $50 billion to bolster infrastructure against cyberattacks and climate change, plus $7.5 billion for electric vehicle charging stations.

Sen. Angus King, an independent who caucuses with the Democrats and was involved in the negotiations, characterized the legislation as “an important first step” in a statement Wednesday night, highlighting the inclusion of $65 billion for broadband.

“These provisions to increase access to high-speed, affordable broadband could very well mean just as much to rural America as electrification did for us generations ago,” King said.

Paying for the package has been a slog throughout the talks after Democrats rejected a plan to bring in funds by hiking the gas tax drivers pay at the pump and Republicans dashed an effort to boost the IRS to go after tax scofflaws.

The final deal could run into political trouble if it doesn’t pass muster as fully paid for when the Congressional Budget Office assesses the details. But Portman said the package will be “more than paid for.”

House Democrats have their own transportation bill, which includes much more spending to address rail transit, electric vehicles and other strategies to counter climate change.

Meanwhile, Democrats are readying the broader $3.5 trillion package that is being considered under budget rules that allow passage with 51 senators in the split Senate, with Vice President Kamala Harris able to break a tie. It would be paid for by increasing the corporate tax rate and the tax rate on Americans earning more than $400,000 a year.

Story by Lisa Mascaro, Kevin Freking and Alam Fram. AP writers Josh Boak and Tali Arbel and BDN writer Jessica Piper contributed to this report.