The latest pushback against President Obama's Iran nuclear deal comes from a group of nearly 200 retired high-ranking U.S. generals and admirals who sent a letter to Congress on Wednesday, voicing their opposition and urging lawmakers to reject the accord.

"The agreement will enable Iran to become far more dangerous, render the Mideast still more unstable and introduce new threats to American interests as well as our allies," the letter states, according to The Washington Post.

Under the Iran deal, negotiated by P5+1 nations and concluded in Vienna last month, Tehran has pledged to halt aspects of its nuclear program in exchange for billions in oil and financial sanction relief. Critics, however, say the agreement is chalk full of loopholes that will practically guarantee Iran will develop nuclear weapons after a decade.

"In our professional opinion, far from being an alternative to war, the Joint Comprehensive Plan of Action makes it likely that the war the Iranian regime has waged against us since 1979 will continue, with far higher risks to our national security interests. Accordingly, we urge the Congress to reject this defective accord," the letter says.

Generals and flag officers from every military branch signed the letter, including Lt. Gen. William G. "Jerry" Boykin, who served as undersecretary of defense for intelligence under President George W. Bush. Retired Vice Adm. John Poindexter and retired Maj. General Richard Secord also signed the letter, both of who were ironically involved in the Iran-Contra affair during which weapons were sold to Iran to fund the Nicaragua contras, reported The International Business Times. The letter was initiated by Leon A. "Bud" Edney, a retired admiral who served as vice chief of naval operations.

Groups both in favor and in opposition of the deal have been rushing to voice their opinion before Congress votes to approve or reject it by Sept. 17.

Last week, three dozen retired senior military officers sent a letter in support of the deal, and earlier this month, 29 of the nation's top scientists also backed what they called a "technically sound, stringent and innovative" agreement, as HNGN previously reported.

Powerful pro-Israel lobby groups plan to spend between $20 million and $40 million advocating against the deal, according to NPR. As of Thursday, more than 980 U.S. rabbis have signed a letter urging Congress to oppose the deal, reported The Times of Israel.

A poll from late July found that most American Jews supported the deal, but more recent polls of the general population indicate that a growing majority of Americans are turning against it.

As most Republican are in ardent opposition, the Republican-led Congress is likely to pass a resolution of disapproval, which would likely prevent Obama from removing U.S. sanctions against Iran. However, Obama promised to veto any such resolution, and his administration has been focusing its efforts on winning over enough Democrats to sustain a veto.

Twenty-nine senators have announced their support for the deal, just five short of the 34 needed to block a veto override. With Senate Majority Leader Harry Reid and Michigan Sen. Debbie Stabenow recently throwing support behind the deal, it appears as though more are soon to follow and the deal will be approved.