(Bloomberg) -- A group of 20 US lawmakers urged President Joe Biden to insist on substantial concessions as his team pursues normalization between Saudi Arabia and Israel, highlighting congressional skepticism about the terms of a possible deal.

The senators, led by Democrats Chris Murphy and Chris Van Hollen, expressed support for normalized ties but questioned why the US should offer Saudi Arabia expanded security guarantees and assistance with the civilian nuclear program it’s seeking, according to a letter Wednesday. They also said Biden must make sure Israel provides “meaningful, clearly defined and enforceable” steps toward a two-state solution with Palestinian leaders. 

The letter, though broadly positive about the impact of a deal in the region, singles out Saudi Arabia as “an authoritarian regime which regularly undermines U.S. interests in the region, has a deeply concerning human rights record and has pursued an aggressive and reckless foreign policy agenda.”

The Biden administration hasn’t given details about its conversations with Saudi Arabia and Israel. People familiar with the matter say the White House is considering defense treaties with both as part of a push to get them to formally recognize each other in a deal the administration hopes could stabilize the restive region.

In a briefing by three senators who co-signed the letter on Wednesday, Murphy said they had been in touch with the administration, both formally and informally, and that they looked forward to a “very robust debate and a set of robust interactions” if a deal ended up before the Senate. 

Read more: A Saudi-Israeli Peace Deal? Who Wants What and Why: QuickTake

The letter was particularly pointed concerning potentially enhanced security ties with Saudi Arabia, reflecting continued anger at the Capitol in the aftermath of the 2018 murder and dismemberment of Washington Post columnist Jamal Khashoggi by Saudi agents inside the nation’s consulate in Istanbul.

“This would be the only security treaty that we have with a non-democracy,” Murphy, a member of the Senate Foreign Relations Committee, told reporters. “The Saudi government has shown very little interest in reforming its brutal methodology of political repression. It is not so long ago that the Senate was debating the Saudi decision, made by top leadership, to kidnap a US resident and chop him into pieces.”

The three senators briefing reporters — Murphy, Van Hollen and fellow Democrat Peter Welch — repeatedly said they wanted to ensure the normalization process came with benefits for the US, especially considering Saudi Arabia’s willingness to hurt American interests by sticking with oil supply curbs.

“If we’re going to have an arrangement with Saudi Arabia, which has had a bad human rights record, where they flirted with China and stick it to us on the oil price, what is in it for us?” Welch said. “We’re asking that question.”

Although the senators conceded in the briefing that the idea of a Palestinian state remains distant, the letter called on the US to secure commitments from Israel that would help achieve the long-term goal of a two-state solution. 

The senators suggest the Biden team get guarantees that Israel wouldn’t annex any part of the West Bank and that it would halt settlement construction and expansion and dismantle “illegal outposts.” They also say Israeli officials should allow the “natural growth” of Palestinian towns and ensure the ability of Palestinians to travel freely. 

(Updates with comments from senators’ briefing starting in fifth paragraph)

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