The Trump administration on Monday proposed cutting billions in discretionary spending in next year’s Department of Transportation budget, while also calling for broad increases in spending over the next decade, a disconnect that left some in Congress and outside groups struggling to interpret the administration’s intentions.

The proposed budget cuts discretionary spending by 13 percent, including deep reductions in spending on Amtrak and airport grants. It also cuts more than $2 billion in highway infrastructure funds and more than $500 million in transit grants.

At the same time, the administration presented what it called a “historic 10-year, $810 billion reauthorization of surface transportation programs,” which would cover highways, transit rail and other programs.

The new $810 billion transportation package would replace a five-year transportation bill, known as the FAST Act, set to expire later this year.

Administration officials acknowledged the wide gap between that long-term proposal and existing funding levels, and did not offer suggestions for closing the gap, saying instead they would work with Congress to do so.

Joel Szabat, the Transportation Department’s acting undersecretary, pointed to the deep shortfall in the Highway Trust Fund, which covers road and transit projects nationwide. The fund’s main source of money, the gas tax, has failed to keep up with inflation or national needs. But the disagreement over whether to raise the gas tax to replenish the fund remains a major sticking point.

“We estimate that there’s $261 billion in additional Highway Trust Fund cash that’s required to support the administration’s proposal over 10 years,” Szabat said.

A Transportation Department official, speaking on the condition of anonymity to describe the administration’s thinking, added that “baseline insolvency under current law is $185 billion. This administration’s policy proposal adds an additional $75 billion on top of this spending.”

Szabat said the administration is “committed to working with Congress on a bipartisan basis to find a responsible way of funding that money going forward.”

While President Trump voiced openness to a gas tax hike earlier in his term, that stance met stiff resistance from conservatives, and the administration has not gotten behind such a move.

Some congressional Democrats, including House Ways and Means Committee Chairman Richard E. Neal (D-Mass.), said they think a bipartisan deal for funding new infrastructure investments is possible, and talks have begun with Treasury Secretary Steven Mnuchin. But skepticism remains strong among some in Congress and the administration itself.

Lana Hurdle, a senior Transportation Department budget official, said the spending plan released Monday “proposes the $810 billion blueprint for the administration’s future surface transportation bill,” but added that “other details and how that will work are all in administration clearance,” including with the White House’s Office of Management and Budget, so officials cannot discuss them.

“Once that review is completed, we’ll be able to give you some more information about the different changes and additions in that proposal,” Hurdle said.

The budget document says the administration will submit a “comprehensive” surface transportation reauthorization proposal “in the coming months.”

Beth Osborne, director of the group Transportation For America, said she’s “trying to figure out the difference” between the administration officials’ long-term proposals and their ideas for short-term cuts. She said she also is trying to understand how officials would pay for their ambitions.

But Osborne said she is already concerned about a number of policies being advanced in the budget documents released Monday, including one she said would undercut efforts to protect pedestrians and bicyclists, who are being killed in increasing numbers.

The administration’s budget “eliminates a required set-aside” for a program known as Transportation Alternatives, according to the proposal. It says that program “restricts States from choosing the most meritorious projects.”

But Osborne said the roughly $850 million in the program this year, which is used to “provide safety infrastructure for people walking and biking,” including crosswalks, sidewalks and bike lanes, represents just a fraction of the billions in overall highway spending.

“Right now, our transportation program is overwhelmingly based on infrastructure that moves vehicles quickly,” and the Transportation Alternatives program is a “very small” effort to help “fix the most dangerous parts,” she said.

But according to the administration’s budget, the proposal would simply give states “additional flexibility” and would allow them to “rehabilitate or expand highways in a manner that supports interstate or regional commerce.”

The Transportation Department official said the “proposal eliminates the mandate that a portion of formula funds be spent by states on these projects and allows them to spend the funds on road and bridge projects as well, if they choose.”

Rep. Peter A. DeFazio (D-Ore.), chairman of the House Committee on Transportation and Infrastructure, assailed administration budget proposals that would cut clean water and environmental programs.

But DeFazio found a possible avenue for optimism.

“One positive aspect of the President’s budget is that it signals he is interested in at least talking about the need to invest in our nation’s crumbling infrastructure,” DeFazio said in a statement.

“But without further details, it’s hard to say whether he is more interested in the status quo or whether he actually wants to move forward with innovative solutions that would tackle carbon pollution in the transportation sector, create jobs and support American manufacturing, and bring our outdated infrastructure into the 21st Century and beyond.”

DeFazio said he is drafting a bill “right now” to do those things, and “I welcome the input of anyone who is truly interested in making our infrastructure smarter, safer, and made to last.”