President Trump's push for a big military buildup in legislation funding the government is likely to go unfulfilled next week, when Congress returns and quickly tries to agree on how to keep the government open after April 28.

A $578 billion bill that funds the Pentagon through September and provides some modest increases has already been hammered out by lawmakers in both chambers and passed by the House. While there is talk of a week-long extension before the big bill is passed, the main bill is likely to be the basis of all defense spending for the rest of the fiscal year.

That means debate over President Donald Trump's promised buildup and the defense budget for 2018 could be shelved until Congress starts working on the fiscal year 2018 appropriations plan. Trump has asked Congress for a $30 billion supplemental spending request for the Defense Department for the rest of the year.

"I think the most likely outcome is an omnibus appropriations bill that includes the defense appropriations bill very similar to what the House has passed," said Todd Harrison, the director of defense budget analysis at the Center for Strategic and International Studies. "That means that the supplemental [request] from the Trump administration is all but dead at this point."

About $25 billion of Trump's request would go into the Pentagon's base budget and would buy more troops, boost critical training such as getting Army brigades ready to deploy, and allow new hardware and facility improvements.

The request also includes $5 billion for overseas war operations, including the fight against the Islamic State group, as well as $3 billion for a wall on the U.S.-Mexico border.

"It represents a critical first step in investing in a larger, more ready, and more capable military force," Trump wrote to Congress last month.

However, even Trump's unfulfilled plan might not be close to what the military needs, according to some.

The military could use more than twice Trump's proposed amount for "shovel-ready" programs such as Navy ship upgrades, Army vehicles and more F-35 Joint Strike Fighters, Mackenzie Eaglen and Gary Schmitt, two residents at the American Enterprise Institute, wrote in a Weekly Standard column published Friday.

"In short, whether the issue is readiness, modernization, or personnel, a supplemental appropriation of $75 billion would not go wasted," they wrote. "To the contrary, it's the essential down payment for the rebuild to follow."

Getting any money at all is expected to be difficult. Trump's proposed $30 billion boost faces major political hurdles on the Hill because it would bust federal budget caps set in law, and would require lawmakers to hammer out a new agreement to lift the limits — an unlikely development with just days until the funding deadline.

"Basically, it seems like a fake request because they almost certainly aren't going to get that," said Benjamin Friedman, a research fellow in defense and homeland security at the Cato Institute.

Still, that does not mean Congress will not agree to some increase for the military. Defense hawks such as Sen. John McCain, R-Ariz., and Rep. Mac Thornberry, R-Texas, are pushing for a big boost and many lawmakers on both sides of the aisle agree the military has been depleted by tight budgets in recent years.

A $5-10 billion increase put into the overseas war budget — a pot of money not subject to federal spending caps — could still be used on base budget needs and remains a possible outcome of the upcoming debate, Harrison and Friedman said.

Some additional money for the military might be needed to ensure the support of lawmakers on the House Armed Services Committee who previously backed the $578-billion defense appropriations bill to fund the military through September.

"Members were convinced to vote for the appropriations bill on promise that a supplemental was coming," said a House staff member close to the negotiations.

It is just one of the many political hurdles still remaining for defense funding. Democratic votes will be needed, especially in the Senate, and the party has insisted that any increased defense dollars be met with increased domestic spending. Conservative Republicans in the House Freedom Caucus also remain a wild card in the negotiations.

Friedman said it is likely that they all eventually settle on passing the $578-billion appropriations bill and possibly a small increase in the overseas war account.

"I think it will dawn on everyone holding out for a very different shaped budget" that the appropriations bill is the best deal they can get for now, he said.