The Republican Senate's consideration of additional Iranian sanctions legislation stems from concerns about the absence of an acceptable agreement with Iran after all these months of negotiations, as well as fears that temporary extensions of limited sanctions relief have allowed the Iranian economy a chance to recover somewhat and has provided material encouragement to potential Iranian economic partners.

The Joint Plan of Action (JPOA) we entered into with Iran prohibits the U.S. from imposing new nuclear-related sanctions such as those contemplated by the Kirk-Menendez bill, and a strong argument can be made that even sanctions with a future effective date would violate the JPOA, thus giving Iran an excuse to end negotiations and blame the U.S. for the breakdown.

But new legislation is unneeded and would be counterproductive. Since 2008, President Obama has repeatedly emphasized that his goal is to prevent Iran from acquiring nuclear weapons and that no options, including the military option, are off the table.

It is likely that the U.S. and Israel cooperated to destroy an Iranian nuclear facility just five months ago, during P5+1 (the U.S., U.K., Russia, China, France and Germany) negotiations with Iran, reinforcing Iran's knowledge that the U.S. and Israel are willing and able to conduct military action against Iran when and if necessary.

Those who question President Obama's credibility can also look at the pain Russia is suffering as a result of U.S. sanctions and the sudden cooperation of our oil-producing allies to lower oil prices at just this moment. New sanctions against North Korea and the temporary shutdown of North Korea's Internet also demonstrate this administration's determination to follow through on its commitments.

Syria today has no chemical weapons thanks to Obama's diplomacy and his credible threat of military action. Obama declared that using chemical weapons was a red line for Syria, and he began lobbying a reluctant Congress for approval to take military action after Syria crossed the line. In the meantime, Obama flooded the Mediterranean with two U.S. aircraft carrier battle groups, totaling approximately 11 ships — ships that could have lobbed cruise missiles into Damascus and Syrian President Bashar Assad's home and headquarters at will.

Consequently, Russian President Vladimir Putin and Assad backed down. The U.S. goal was not to drop bombs. The U.S. goal was to use the threat of military force to achieve its objective, and that objective was achieved through diplomacy. Meanwhile, despite initial fears that the Islamic State in Iraq and Syria (ISIS) would spread throughout the Middle East, its progress has been checked, in large part because of American air power and U.S.-trained Iraqi regulars, Kurds and certain Syrian rebel groups. And is it a coincidence that plunging oil prices, which are hurting Iran, Russia and other enemies of the U.S., just happen to come at a time when oil-producing allies such as Saudi Arabia would most benefit from a deal preventing Iran from acquiring nuclear weapons?

Now is not the time for additional sanctions legislation. Obama and Secretary of State John KerryJohn Forbes KerryShould President Trump, like President Obama, forsake human rights in pursuit of the deal with a tyrant? GOP Senate report says Obama officials gave Iran access to US financial system Democrats conflicted over how hard to hit Trump on Iran MORE have been clear that not only that Iran will be prevented from acquiring nuclear weapons, but that no deal is better than a bad deal. We don't have a deal now because the administration refused to sign off on a bad deal. Speculation about where the parties were is just that — speculation — and should be viewed with skepticism coming from anyone not directly involved in the negotiations. The fundamental negotiating principle is that nothing is agreed to until everything is agreed to.

America should continue to negotiate an agreement that is good for the U.S., Israel and the world, backed by a credible threat to use force should negotiations fail. Premature enactment of additional sanctions legislation would violate the JPOA, which would disrupt our international coalition and probably cause Iran to renege on its commitments under the JPOA, thus stealing defeat from the jaws of possible victory.

Iran, which is already suffering from crippling economic sanctions (exacerbated by the recent plunge in oil prices) already knows that Congress will pass even tougher sanctions if there is no deal, and that Obama knows how to use and is committed to using American military power to prevent Iran from acquiring nuclear weapons.

Congress does have a role to play, but its role is not to sabotage negotiations with unwise legislation. Congress is institutionally incapable of micromanaging foreign policy. Sanctions alone will not prevent Iran from acquiring nuclear weapons. Sanctions didn't stop Iran from getting to where it is today, but sanctions did get Iran to the negotiating table where, in exchange for limited, temporary and easily reversible sanctions relief, Iran stopped or rolled back key elements of its nuclear program.

Should the talks fail, Congress could authorize (to the extent authorization is needed) U.S. military action against Iran, as well as additional economic and diplomatic sanctions.

In the meantime, Congress would best serve the American people by seeking to understand, rather than seeking to scuttle, the diplomacy that remains our best hope of thwarting Iran's nuclear ambitions.

Sheffey has long been active in the pro-Israel community and in Jewish communal life. He is a lifelong member of AIPAC (the American Israel Public Affairs Committee) and served on the board of CityPAC, a pro-Israel Chicago-based political action committee, for seven years, including two years as its president. He is also active in Democratic politics and served as an elected delegate to the 2012 Democratic Convention from Illinois.