Families of American hostages still being held in Gaza joined U.S. lawmakers on Capitol Hill on Tuesday to push strongly for the Israeli-approved hostage deal laid out by President Joe Biden last week, emphasizing that the onus is on Hamas to finalize the deal.

Jonathan Dekel-Chen, father of Sagui Dekel-Chen, said in a roundtable with House lawmakers that “there is more than enough evidence to show that this deal that has been offered by Israel and supported by the United States… is probably the best, last chance to get any of our loved ones, and any of the 124 hostages who still remain in Gaza.”

Dekel-Chen emphasized that the burden is on Hamas to approve the deal, saying that “the time is now for Hamas to prove that its real interests are for the people of Gaza, and not just for the killing of Jews and Israelis.”

The families met earlier in the day with National Security Advisor Jake Sullivan at the White House. Dekel-Chen said that there’s “some reason for optimism — not because anyone is optimistic about Hamas’ potential answer, but that it’s all on the table.”

He added that, in presenting the plan publicly, Biden had created “more clarity about who’s to blame from continued warfare.”

Dekel-Chen’s message about Hamas was echoed by the other hostage families and lawmakers.

“We need Hamas to get to a yes,” Ruby Chen, father of Itay Chen, said. “And the U.S. advocating for that development, and Congress to do whatever they can to make sure that we get a yes, in order to get this deal going, in order for us to be able to move on with our lives,”

Ali Alexander, father of Idan Alexander, said the current moment is a “perfect storm” for a deal, and that everything hinges on Hamas’ reply. “So we’re advocating for that, putting additional pressure on all the regional partners in the Middle East,” he said.

Aviva Siegel, who was released as part of a previous hostage deal and whose husband, Keith Siegel, remains in Hamas captivity, said that Biden’s announcement “gave me hope” and that she’s hopeful “the United States is going to be strong enough to bring Keith home alive.”

Rep. Elissa Slotkin (D-MI), who is running for her state’s Senate seat, said she had been at the White House earlier Tuesday morning speaking to a negotiator departing shortly for hostage talks in the Middle East, and agreed that it is a “perfect storm.”

“We’ve had a bunch of parties in Israel come forward and say they support the deal. And the deal is strikingly similar to what Hamas itself put up five weeks ago,” Slotkin said. “So at this point, if they don’t take it, it’s just to prolong the suffering of their own people for their own purposes.”

She also expressed frustration about the situation that the hostages’ families are in, where those working to free their loved ones are “negotiating with someone who’s not an equal actor, who’s not a fair actor, who’s not a responsible actor.”

Rep. Brad Schneider (D-IL) likewise expressed frustration with the unequal pressure on Hamas and Israel.

“There’s 1,001 organizations, populations putting pressure on Israel, no one is putting pressure on Gaza, on Hamas,” Schneider said. “We have to make sure Hamas not only feels that pressure but that Hamas knows that their future is not controlling Gaza and holding those hostages.”

Rep. Haley Stevens (D-MI), who co-leads the congressional hostage task force and organized the roundtable, also expressed frustration with actions from the international community she said were unproductive.

“Outrageous that the ICC has criminally charged Hamas and the democratically elected leadership of Israel. Unbelievable,” Stevens said, referring to the International Criminal Court’s arrest warrants. “What is that getting us? Is that getting us the hostages home?”

She said that “Israel is blamed for an attack that happened to them, and innocent people. Israel is over-litigated, over and over and over again. I don’t even turn on the cable news, because it’s too frustrating to watch.”

But she said the stories of the hostages have helped to break through those narratives.

Rep. Dan Goldman (D-NY) emphasized that Israel had put this deal forward, adding, “Whatever the political consequences of this offer in Israel are [are] necessary consequences for doing the right thing to bring your home your loved ones.” He acknowledged that “Israel has moved very far to agree to” the deal, adding that “Israel must stand by this agreement.”

Some members of Prime Minister Benjamin Netanyahu’s governing coalition have threatened to withdraw if the deal proceeds, which could collapse the government.

“The international pressure right now must be on Hamas to accept this deal, for everyone who wants an end to this conflict,” Goldman continued. “There is one person who can bring an end to this conflict, and that is [Hamas leader Yahya] Sinwar… Everyone’s pressure must be put on Hamas to accept this deal.”

Rep. French Hill (R-AR), the co-chair of the hostage task force, said, “This is a deal that’s been on the table, and when it’s been rejected, it’s been rejected by Hamas… The position of the United States should be unequivocal to back Israel in the work they’re doing and demanding the freedom of the hostages.”

He also noted that Sinwar, the Hamas leader in Gaza, had been freed as part of a previous hostage deal.