WASHINGTON — Senate leaders announced Wednesday they have sealed an agreement on a two-year budget pact that would shower both the Pentagon and domestic programs with almost $300 billion above existing limits, giving wins to both GOP defense hawks and Democrats seeking billions for infrastructure projects and combating opioid abuse.

The agreement is likely to be added to a stopgap spending bill that passed the House on Tuesday, aimed at averting a government shutdown Thursday at midnight. Democratic leader Chuck Schumer of New York called the Senate agreement “a genuine breakthrough.”

However, it would not resolve the plight of immigrant “Dreamers” who face deportation after being brought to the U.S. illegally as children. As the Senate leaders were announcing their agreement, Minority Leader Nancy Pelosi of California was holding the floor in the House, declaring she would oppose the measure unless her chamber’s GOP leaders promised a vote on legislation to protect the younger immigrants.

That introduced doubts as to whether the plan could pass in the House, where prominent GOP conservatives are also opposed to the higher spending.

The Senate agreement also contains almost $90 billion in overdue disaster aid for hurricane-slammed Texas, Florida and Puerto Rico.

It would increase the government’s borrowing cap to prevent a first default on U.S. obligations that looms in just a few weeks.

The night before, the House passed legislation to keep the government running through March 23, marrying the stopgap spending measure with a $659 billion Pentagon spending plan, but the Senate plan would rewrite that measure.

Senate Democratic leaders have dropped their strategy of using the funding fight to extract concessions on immigration, specifically on seeking extended protections for the “Dreamer” immigrants. Instead, Senate Minority Leader Schumer, D-N.Y., went with a deal that would reap tens of billions of dollars for other priorities while hoping to solve the immigration impasse later.

The budget agreement would give both the Pentagon and domestic agencies relief from a budget freeze that lawmakers say threatens military readiness and training as well as domestic priorities such as combating opioid abuse and repairing the troubled health care system for veterans.

The core of the agreement would shatter tight “caps” on defense and domestic programs funded by Congress each year.

They are a hangover from a failed 2011 budget.