Senate Republicans unveiled their latest infrastructure counteroffer on May 27, shortly before President Biden's informal deadline of Memorial Day.

The plan calls for a $928 billion investment over the course of eight years. Here's whats in the proposal:

• $506 billion for roads, bridges and major projects, including $4 billion for electric vehicle infrastructure

• $98 billion for public transit systems

• $46 billion for passenger and freight rail

• $21 billion for safety

• $22 billion for ports and waterways

• $56 billion for airports

• $22 billion for western water storage

• $72 billion for water infrastructure

• $65 billion for broadband infrastructure

• $20 billion for infrastructure financing

"It's a serious effort to try to reach a bipartisan agreement," said Sen. Shelley Moore Capito (R., W.V.), who is leading the Republican infrastructure effort.

The Biden administration offered Republicans a $1.7 trillion infrastructure proposal last week, down from $2.3 trillion — but Republicans rejected the plan, saying it was "well above the range of what can pass Congress with bipartisan support." Republicans had originally offered a $568 billion proposal focused on traditional infrastructure projects.

The White House has called for more investments in clean energy, workforce training, the care economy and industries of the future. In a press conference on Thursday morning, Senate Republicans stressed they were not going to expand their proposal beyond physical infrastructure projects and broadband.

"I would say that is probably the big question — the scope," said Capito. "We haven't been satisfied, I don't think, with the White House's response to our first initial ask on narrowing the scope."

While the White House did remove portions of its research & development and manufacturing measures for its bill, many of those proposals are already included in a separate bill designed to boost U.S. competition with China.

"We want to focus on actual infrastructure. The platforms and services that move people and goods and services through our economy. That's what people understand to be infrastructure and we can reach an agreement if we focus on those items," said Sen. Pat Toomey (R., Pa.).

In a statement, White House Press Secretary Jen Psaki said the topline number increase was encouraging and had "several constructive additions."

"At the same time, we remain concerned that their plan still provides no substantial new funds for critical job-creating needs, such as fixing our veterans’ hospitals, building modern rail systems, repairing our transit systems, removing dangerous lead pipes, and powering America’s leadership in a job-creating clean energy economy, among other things," said Psaki.

How to pay for an infrastructure plan will also be a major hurdle. Republicans have made it clear they do not want to raise taxes on businesses or alter the 2017 tax cuts at all, while President Biden has called for tax hikes on corporations.

"We're not raising taxes," said Toomey. "We believe the 2017 tax reform contributed significantly to enabling us to achieve the best economy of my lifetime."

Republicans have suggested repurposing unused COVID relief funding to help pay for infrastructure projects.

"We are concerned that the proposal on how to pay for the plan remains unclear: we are worried that major cuts in COVID relief funds could imperil pending aid to small businesses, restaurants and rural hospitals using this money to get back on their feet after the crush of the pandemic," said Psaki.

A bipartisan group of senators is also working on another infrastructure proposal in case negotiations between the White House and Senate Republicans fail. While President Biden has said he wants the infrastructure package to be bipartisan, Democrats could move attempt to pass an infrastructure package without Republicans through the reconciliation process if negotiations fail.

Capito told reporters using the reconciliation process would "be destructive to our future bipartisan attempts."

The U.S. Chamber of Commerce called the Republican proposal a "significant step forward" and warned against a partisan infrastructure package.

"Fundamental, durable policy is not achieved when one political party pushes through legislation on their own. We urge continued bipartisan discussions so our nation’s infrastructure receives the modernization it desperately needs," said Neil Bradley, U.S. Chamber of Commerce Executive Vice President and Chief Policy Officer.

Psaki said the White House will continue working with lawmakers throughout the next week.

Jessica Smith is chief political correspondent for Yahoo Finance, based in Washington, D.C. Follow her on Twitter at @JessicaASmith8.

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