WASHINGTON (AP) — Build more wall. Reinstate Trump-era immigration policies. Or simply shut down the U.S.-Mexico border.

Congressional Republicans argue that President Joe Biden already has all the authority he needs to halt the flow of migrants through the U.S.-Mexico border. They’re making the claim as a bipartisan deal that the president negotiated with senators to expand his authority is facing near-certain defeat.

The reality about Biden’s powers to control migration is far more complicated.

Without changes to immigration laws or more funding to manage the growing number of migrants arriving at the Southern border, not much of what Biden can try will stick — just as was the case for presidents before him.

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“President Biden needs Congress to be able to address the situation at the border,” said Kathleen Bush-Joseph, a lawyer and policy analyst at the nonpartisan Migration Policy Institute. “That is the simplest way to put it.”

The $118 billion bipartisan proposal in Congress would overhaul the asylum system to provide faster and tougher enforcement, as well as give presidents new powers to immediately expel migrants if authorities become overwhelmed with the number of people applying for asylum. It also would add $20 billion in funding — a huge influx of cash.

The package, which pairs border enforcement policy with wartime aid for Ukraine, Israel and other U.S. allies, would be the most significant immigration legislation in a decade. It has the potential, for better or worse, to transform some of the most vexing border problems. And up until recently, it appeared to have a chance at passing. Donald Trump’s allies are looking to sink the deal in large part because the Republican presidential frontrunner is loathe to give Biden a win on immigration. Trump wants to hammer the president on the issue during the campaign.

“Just months ago, Republicans were asking for this exact bill to deal with the border, to provide support for Ukraine and Israel. And now it’s there. And they’re saying, ‘Nevermind. Nevermind,” Biden said Tuesday.

House Speaker Mike Johnson said Tuesday he would not put the bill on the House floor in its current form, saying it would act as a “magnet” for illegal immigration, the authority to shut down asylum was “riddled with loopholes” and that the release of migrants into the U.S. would only continue.

“If you give extraordinary authority to the very architect of the catastrophe, it will do no good,” Johnson said.

Elise Stefanik, a New York Republican posted on X, formerly Twitter: “Biden has the power to end the border crisis without Congress. He just doesn’t want to.”

But immigration officials do not have expanded detention capability unless they get more funding for detention. They also can’t hold families in detention longer than roughly three weeks under a longstanding policy, and they can’t mix together single adults and family units for safety reasons under law.

Biden already has flexed his unilateral powers to address the border in multiple ways.

The Biden administration has taken more than 500 executive actions on immigration since he took office, according to the Migration Policy Institute, more than Trump did in four years as president. Some policies have been successful, but the number of crossings has continued to rise to record numbers.

His administration’s approach has been to pair new humanitarian pathways for migrants with a crackdown at the border to try to discourage migrants from making the dangerous journey to the U.S.-Mexico border on foot. He also has tried to make the issue more global, using his foreign policy experience to broker agreements with other nations.

And the administration has worked to restrict asylum through a proposed federal rule. But that policy is currently tied up in litigation, much like what stymied Trump during his tenure. A law change by Congress would make those lawsuits less frequent and less successful, and an infusion of cash would make it possible to hire more employees to dig out from the backlog.

“Just point blank, that Biden could do this on his own is just not true. There’s simply not enough asylum officers,” said Taylor Levy, a longtime immigration attorney who has spent years at the U.S.-Mexico border.

Biden could say he was going to shut down the U.S.-Mexico border entirely, but there would be billions of dollars lost or delayed in trade, and the U.S. would be in violation of international laws that govern what a country must do with refugees.

As for some of the other policies, they’re also not likely to be easily reinstated even if Biden wanted to, which he doesn’t.

The Title 42 policy rolled out by Trump relied on special powers granted a president during a public health emergency. It allowed border agents the ability to turn away many asylum seekers immediately. Those powers went away when the national emergency over the pandemic was ended by Congress last May.

The so-called “ Remain in Mexico” policy put in place by the Trump administration forced asylum seekers to wait out their claims in Mexico in squalid camps riddled with crime and sickness. But that agreement relies on cooperation from Mexico, and President Andrés Manuel López Obrador is hinting that talks with the U.S. on migration could suffer after reports of a U.S. investigation into suspected drug money donations for his 2006 campaign. On Tuesday he said he finally agreed to meet with a top White House adviser only after he got a call from the president.

As for the border wall, Trump tried to build some without Congressional approval. He declared a national emergency so that he could divert billions of federal dollars from military construction and other purposes after Congress approved only a fraction of the money he had demanded. The issue was challenged in court almost immediately and went all the way up to the U.S. Supreme Court.

Anna Cabot, immigration clinic director at the University of Houston Law Center, said reimposing Title 42 rules would require action by the director of the Centers for Disease Control and Prevention and some sort of justification, like the coronavirus. Even then, it would face litigation. As for the Remain in Mexico policy and “emergency” border wall construction both would “immediately be tied up in most likely losing litigation,” she said.

The bipartisan bill has earned a wide range of support, including from the Border Patrol union, though some Democrats and immigrant advocates say it’s far too restrictive and would change the U.S. role as a haven for refugees.

But Biden has said it was the best effort so far to stop the continued flow of migrants that are straining an already broken system.

He went so far as to adopt Republican language, saying he’d “shut down the border” when he was given the authority to do so. And on Tuesday, he questioned why it appeared Congress was not willing to give him the tools to manage the growing numbers at the border and accused Republicans of being too afraid to stand up to Trump on an issue critical to the country and also to the world.

“Republicans have to decide. Who do they serve? Donald Trump or the American people?” he asked.

___ Associated Press Writer Mark Stevenson in Mexico City contributed to this report.