WASHINGTON (AP) — White House chief of staff Jeff Zients recently heard from a powerful Democratic senator that steep levels of migration at the U.S.-Mexico border had become, in a word, untenable.

Illinois Sen. Dick Durbin, the No. 2 Democrat, had signed onto a statement denouncing "reports of harmful changes to our asylum system" that were being proposed as part of a border deal on Capitol Hill. Yet Durbin, a veteran of numerous immigration battles, had also received concerning briefings from border officials and seen firsthand how the rising number of asylum-seekers had overwhelmed resources in his Midwestern state.

So when Zients dialed Durbin one weekend this month for a temperature check on the ongoing border talks, the senator was candid.

"I told him I thought the current situation is unsustainable, and the Democrats need to be part of the solution," Durbin said. President Joe Biden's top aide signaled the White House felt the same way, stressing to Durbin that "we have to engage with the Republicans and see if there's some middle ground," according to the senator's retelling.

That conversation between Zients and Durbin is just one of the several calls that the White House chief of staff has been making to key lawmakers in recent days, underscoring how top Biden administration officials have considerably ramped up their involvement with Capitol Hill as the fate of Biden's emergency spending request for Ukraine remains in the balance.

Homeland Security Secretary Alejandro Mayorkas, along with senior officials from the White House and the Department of Homeland Security, have spent hours behind closed doors haggling over the intricacies of immigration policy alongside senators trying to reach a border deal. Zients himself dropped by one of those meetings at the Capitol last week, reiterating to the negotiators Biden's plea to find a solution.

And the White House chief of staff has been talking regularly with Oklahoma Sen. James Lankford, the chief GOP negotiator. It's a level of engagement that has heartened Republicans who had pushed for Biden to get more involved.

Republicans, who control the House and can block legislation in the Senate, say a deal is not possible without significant White House buy-in. Having Biden's senior aides actively participate in the talks sends a message — particularly to wary Democratic lawmakers — that the president is willing to cut a border deal that could make some in his own party uncomfortable.

And any deal that is reached on the border could also help address one major political liability for Biden as he gears up for his reelection, particularly if the increased involvement by the White House helps the public see the president as someone seeking a solution to the rising border numbers.

"I think an important change is that we now have all the entities at the table," said Sen. Kyrsten Sinema, I-Ariz., one of the lawmakers who for weeks has been negotiating a border deal. "The White House is involved in these negotiations as a full partner, and that's important. It shows a level of seriousness and intention to solve this crisis."

Another major reason why the White House and senior administration officials have gotten so directly involved is the sheer complexity of immigration law and the Department of Homeland Security's central role in implementing any restrictions that Congress will write.

Still, this wasn't the White House's strategy from the start.

Once it became clear congressional Republicans would demand policy extractions in exchange for releasing billions in additional aid for Ukraine, the White House intentionally hung back from the negotiations — replicating its past strategy of letting the legislators legislate, which had led to several of Biden's priorities becoming law. Though administration officials had been aware of what was being discussed, they deferred to the senators leading the talks — Lankford, Sinema and Sen. Chris Murphy, D-Conn.

That dynamic changed this month. Mayorkas has been a consistent presence in the negotiations, along with White House legislative affairs director Shuwanza Goff and Natalie Quillian, a White House deputy chief of staff who has taken immigration under her portfolio. They, along with the senators and a coterie of other senior aides, have negotiated for hours daily, and continued to do so on Capitol Hill throughout the weekend.

Outside of the negotiating room, Zients has talked regularly with Senate Majority Leader Chuck Schumer, D-N.Y., and the other negotiators. When the chief of staff has spoken to Lankford, he has urged him and other Republicans to stick with the border negotiations because aid for Ukraine is so vital, according to an administration official.

"We can't finalize any kind of agreement until the White House is actually engaged," said Lankford, who stressed that having Biden's aides in the room has been helpful. "There's a lot of Senate Democrats that are wondering, 'What's the White House think about this?' That's a reasonable thing for them to ask. Can't answer until they're actually there."

The stakes of the negotiations — being held in a room on the second floor of the Capitol, near Schumer's suite of offices — are enormous for the White House and for Biden's foreign policy legacy. Entangled with the border talks are not only additional funds for Ukraine but also for Israel, which has engaged in a violent combat in Gaza since an Oct. 7 assault by Hamas militants killed more than 1,200 Israelis.

Biden and White House aides have repeatedly warned, in dire terms, about the consequences of letting Ukraine funding run dry. The president said earlier this month that "any disruption in our ability to supply Ukraine clearly strengthens Putin's position," and administration officials have stressed that the money to aid Kyiv will run out by the end of the year.

Yet other Democrats and immigrant-rights advocates have been concerned that Biden's desperation for Ukraine aid would cause the White House to accept hardline policies restricting avenues for asylum that it would otherwise not support. And it has fallen to senior White House aides to take incoming fury from upset lawmakers. Zients and Mayorkas spoke with members of the Congressional Hispanic Caucus on Saturday, during which several Democrats raised concerns about the ongoing border talks.

"I think there's this view sometimes because a lot of senators become president, that you could just have the White House and the Senate come up with a deal and somehow jam the House," said Rep. Ro Khanna, D-Calif., a leading progressive, on "Fox News Sunday." "But the House is still the people's house, and we're going to have our say. We need to be involved."

___

Associated Press writer Stephen Groves contributed to this report.