National Security Adviser Jake Sullivan did not rule out the possibility of President Joe Biden sending aid to Israel with conditions in an interview on NBC News’ “Meet the Press” Sunday, amid a four-day temporary cease-fire in the Israel-Hamas war with more hostages expected to be released.

Health officials in Gaza said more than 14,500 have died and more than 1.7 million have been displaced after weeks of Israeli attacks. The Israel Defense Forces estimate 1,200 people were killed in the Oct. 7 Hamas attack, with more than 200 people held hostage in Gaza.

Amid pressure from some Democrats who have expressed empathy toward Palestinians, Biden had said during a recent press gaggle that the question of aid to Israel with conditions is a “worthwhile thought.”

Asked by NBC’s Kristen Welker if the administration would support that, Sullivan said: “In that answer, President [Joe] Biden acknowledged that idea but he went on to say that his approach — President Biden’s approach, which was high-level private diplomacy — has actually generated results.”

Pressed by Welker to clarify if Biden is “open to signing legislation that would provide aid to Israel that comes with conditions,” Sullivan did not rule it out.

“He is going to continue to focus on what is going to generate results,” Sullivan said. “And as he said in the press conference quite clearly, and as you can see from the fact that for the last few days we’ve seen hostages released, the approach that he is taking — direct presidential diplomacy behind closed doors with the Israelis and with our Arab partners — that’s what’s generating the kinds of results that we’re seeing right now.”

Biden has faced mounting pressure from some congressional progressives, who have warned that they would not support aid to Israel without conditions intended to reduce civilian casualties, including that the Israeli Defense Forces’ ease its bombardment of Gaza.

In a New York Times op-ed published last week, Sen. Bernie Sanders, I-Vt., said that although the U.S. has provided Israel a “substantial” amount of aid in its war with Hamas, the “blank check approach must end.”

“The United States must make clear that while we are friends of Israel, there are conditions to that friendship and that we cannot be complicit in actions that violate international law and our own sense of decency,” he wrote. “That includes an end to indiscriminate bombing; a significant pause to bombing so that massive humanitarian assistance can come into the region; the right of displaced Gazans to return to their homes; no long-term Israeli occupation of Gaza; an end to settler violence in the West Bank and a freeze on settlement expansion; and a commitment to broad peace talks for a two-state solution in the wake of the war.”

Sullivan also noted on “Meet the Press” that Biden is scheduled to speak with Israeli Prime Minister Benjamin Netanyahu on the phone Sunday.

“President Biden has been on the phone just in the last 24 hours with the emir of Qatar. He will be speaking today with the prime minister of Israel,” he said. “So he’s continuing to work this hour by hour to see if we can secure those additional days of pause and those additional hostages coming home to their families.”

In total, 50 of an estimated 240 people taken by militants in the Oct. 7 Hamas attack and 150 Palestinians held by Israel are expected to be released by the end of the cease-fire and hostage exchange between Israel and Hamas Monday.

On Saturday, 13 Israelis and four Thai citizens were released from Gaza as part of a deal, bringing the total to 26 Israelis freed from Gaza. Under the agreement, 39 Palestinian prisoners held by Israel were also released on the second day of the truce.

Sullivan said during his morning interview that the Biden administration had “reason to believe” one American hostage could be among those released on Sunday, the third day of the temporary cease-fire.

“The initial hostage deal involves the release of women and children, and there are three Americans in that category: two women and one young child. And we have reason to believe that one of those Americans will be released today,” he said, adding that the U.S. is “hopeful” that more Americans will be released in the coming days.

Later Sunday, 17 hostages were released by Hamas, including 4-year-old American Abigail Edan, according to a list from Prime Minister Benjamin Netanyahu’s office, on the third day of the truce. Of the 17, three were foreign nationals, the statement added.

Edan, an American girl who turned 4 in captivity, “tragically lost her parents” in the war, Sullivan said.

House Intelligence Committee Chair Mike Turner, R-Ohio, on Sunday morning criticized Sullivan and the Biden administration for not providing more details about the remaining U.S. hostages, suggesting that they may not have obtained such information.

“No one really knows the number [of hostages]. And Jake Sullivan was saying that he doesn’t even know the number, nor do we know the proof of life. And you would have thought this if they’re claiming credit — this is a Biden deal — that those are details that we would have conditioned this process through,” Turner said.