Twenty U.S. senators on Wednesday urged U.S. President Joe Biden to preserve the option of a two-state solution in any potential Israel-Saudi Arabia normalization agreement, further detailing their concerns with Riyadh's demands from the U.S.

The letter - led by Sens. Chris Murphy, Chris Van Hollen, Senate Majority Whip Dick Durbin and Peter Welch - is the most detailed elaboration from the Democratic Party on Biden's efforts to date, showcasing the uphill climb the president faces in hopes of securing domestic support for his efforts.

"There's a version of this agreement that's good for the United States, and there's a version that could run contrary to our security interests in the region," Murphy said ahead of the letter’s release.

Van Hollen added "the question that comes here is: what kind of commitments does the United States have to make to facilitate normalization? And what kinds of commitments should we be asking other parties in return while we make important commitments?"

"I don't think any of us are under any illusions that we're going to be close to achieving a two-state solution anytime soon, but if that is the ultimate goal of American policy, we need to make sure that changes on the ground don't make that even harder than it already is," he added.

"Peace between Israel and its neighbors has been a longstanding goal of U.S. foreign policy, and we are maintaining an open mind about any agreement that would potentially deepen the political, cultural and economic ties between Saudi Arabia and Israel," the senators wrote, while noting the agreement may require Senate action.

They were joined on the letter by Sens. Tammy Baldwin, Tom Carper, Tammy Duckworth, John Fetterman, Martin Heinrich, Tim Kaine, Ben Ray Lujan, Ed Markey, Jeff Merkley, Patty Murray, Jon Ossoff, Bernie Sanders, Brian Schatz, Jeanne Shaheen, Raphael Warnock and Elizabeth Warren."We are concerned about reports that Saudi Arabia is requesting a security guarantee from the United States in exchange for normalization with Israel. Historically, security guarantees through defense treaties have only been provided to the closest of U.S. allies: democracies that share our interests and our values," the senators write.

They note the U.S. has long refrained from committing itself to treaty-backed security guarantees in the Middle East.

"A high degree of proof would be required to show that a binding defense treaty with Saudi Arabia – 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 – aligns with U.S. interests, especially if such a commitment requires the U.S. to deploy substantial new permanent resources to the region," they stress.

The senators further note how Saudi Arabia is reportedly seeking U.S. support to develop a civilian nuclear program, and to purchase more advanced U.S. weapons.

"While we should seriously consider whether it is in U.S. interests to help Saudi Arabia develop a domestic nuclear program, we should always maintain the high bar of the 'gold standard’ 123 Agreement and insist on adherence to the Additional Protocol," they write, adding that the Yemen war demonstrated that providing more advanced weaponry to Saudi Arabia "should be done with careful deliberation to ensure that such equipment only be used for truly defensive purposes and does not contribute to a regional arms race."

They further stressed the agreement should include "meaningful, clearly defined and enforceable provisions to achieve your stated objective of preserving the option of a two-state solution to the Israeli-Palestinian conflict and to ensuring that there be 'equal measures of dignity and security’ for both Israelis and Palestinians."

They note this should include a commitment by Israel not to annex any or all of the West Bank; to halt settlement construction and expansion; to dismantle illegal outposts, including those that have been retroactively 'legalized’; and to allow the natural growth of Palestinian towns, cities and population centers and the ability to travel without interference between and among contiguous Palestinian areas.

"These elements are essential to any sustainable peace in the Middle East and to preserving Israel’s own future as a Jewish, democratic state," they write, adding "as the parties make requests of the U.S. throughout your discussions, we hope that you will also seek commitments from them with respect to actions they can take to further U.S. national security interests and peace and stability in the region."

Saudi Arabia’s reported demands will likely require a two-thirds majority in the Senate, and some may require a similar majority in the House of Representatives as well. The Senate is currently split evenly between the parties, with the Democrats holding the tiebreaker, while the Republicans hold a minuscule majority in the House.

While there are very few senators who are theoretically against the general idea of Israeli-Saudi normalization, many will have watched warily as the Biden administration has mulled giving both leaders potentially career-defining achievements at a time when they have been effectively deemed persona non grata in Washington.