Biden is getting closer to a deal with Iran, and Democrats in Congress need to get with the program

• Biden has a narrow window of opportunity to prevent a new nuclear crisis with Iran.
• To restore the 2015 nuclear deal, Biden needs Congress' support, including that of hawkish Democrats.
• Thomas M. Countryman is chairman of the Arms Control Association and a former assistant secretary of state for international security and nonproliferation.

Amid growing rumors that the US's return to the JCPOA is now a "when" and not "if" scenario, it is critical that Congress supports President Joe Biden as he progresses closer to restoring US and Iranian compliance with the 2015 multilateral deal.

Biden has a narrow window of opportunity to prevent a new nuclear crisis with Iran - a situation created in 2018 when former President Donald Trump unilaterally withdrew from the agreement - and congressional support from Democrats will help ensure diplomacy is victorious.

The JCPOA closed all pathways by which Iran could secretly build nuclear weapons. It is the best mechanism we have in stopping a new global nuclear crisis and preventing another devastating war in the Middle East.

With the Democrats in control of both chambers of Congress and the White House, it seems like Biden would have the support to continue on his path of reversing the egregious errors of the maximum pressure campaign adopted by the previous administration.

And he does, somewhat. Back in December, over 150 members of the House endorsed a rapid return to the deal. And just this month, a group of more than two dozen senators led by Sen. Tim Kaine (D-Virginia) and Sen. Christopher Murphy (D-Connecticut), called on the president "to return to the JCPOA and use a 'compliance for compliance' approach as a starting point to reset US relations with Iran."

But unfortunately, Biden's pragmatic approach - which benefits US security and nonproliferation interests - does not have the full support of Democrats in the Senate, including Sen. Bob Menendez, Democratic chairman of the Foreign Relations Committee and he is trying to take other Democrats with him.

Menendez has gone out of his way to undermine Biden's diplomacy by joining forces with Republican Sen. Lindsey Graham - a stalwart Trump ally - to press the Biden administration to maintain existing sanctions against Iran.

Menendez, Graham and their allies believe that the sanctions will leverage a more ambitious and comprehensive agreement that extends current limits on Iran's nuclear program, adds new restrictions on Iran's ballistic-missile program, and somehow addresses Tehran's disruptive actions in the region, including its support for proxy militias hostile to US allies.

That may sound good on paper, but it is unrealistic, counterproductive, and would be a continuation of the failed policy of Donald Trump. There is no path to resolving those important issues that does not begin with a restoration of the 2015 agreement that Trump violated.

Pressure and punishment through sanctions are not the same as "leverage." In the real world of diplomacy, a key component of leverage is "credibility."

US diplomatic credibility on the Iran issue took a plunge during the Trump years, particularly after he unilaterally pulled out of the JCPOA in 2018 even though Iran was complying with the deal. All the pressure in the world won't accomplish your goals if the other side, and your best allies, have no reason to believe you will keep your word.

Trump's irresponsible decision in 2018 to withdraw from the nuclear deal and reimpose sanctions lifted by the accord - despite the fact that Iran was in full compliance with the agreement and despite the objections of key US allies - unsurprisingly led Tehran to retaliate by breaching some of the deal's limits on its nuclear activities beginning in 2019.

Now, the time it might take Iran to amass enough material for a bomb has been reduced from one year or more, under the 2015 agreement, to perhaps less than three months.

If the US and Iran can agree on a process to return to compliance in their ongoing talks in Vienna, there is hope that Iran's most worrisome nuclear violations can be reversed, and the nonproliferation benefits of the 2015 accord can be quickly restored.

But just this week, Menendez is once again attempting to throw a wrench in the gears of diplomacy. He, along with Sen. Jim Risch, a known Iran hawk, introduced a bill that would purposefully complicate the diplomatic process by adding untenable reporting requirements for international agreements.

Biden needs a solid foundation for further negotiations with Iran to try to secure a follow-on deal that strengthens and lengthens the original nuclear agreement and advances America's interests in the region.

Democrats in the Senate should join Biden, many of his fellow members of Congress, and our key European allies in recognizing Trump's policy was a failure. The first step toward curtailing Iran's nuclear program and keeping the regime as far away from nuclear weapons as possible is for both sides to quickly return to compliance with the original 2015 nuclear deal.

There is no shortcut to broader goals, and "maximum pressure" is not a substitute for hard-nosed diplomacy.

Thomas M. Countryman (Twitter: @TMCountryman) is chairman of the Arms Control Association and was assistant secretary of state for international security and nonproliferation from 2011 to 2017.