The New York Times website published the text of this letter on Thursday. The letter referred to concerns that have been raised about the ability of the agreement to prevent Iran from obtaining a nuclear weapon, as well as its impact on the ability of the West to counteract Iran’s destabilizing efforts in the region.

In its three pages, the letter assures Nadler and his colleagues that the Obama administration stands ready to use “all of the options available to the United States – including the military option” – to restrain Iran attempt to break out to nuclear weapons capability. It also declares the president’s intention to create an office within the State Department to oversee implementation and enforcement of the Joint Comprehensive Plan of Action.

Obama’s latest publicized act of outreach to undecided Democrats comes amidst rising skepticism not only about the JCPOA itself but also about side deals between Iran and the International Atomic Energy Agency, which many believe will have an impact on verification of Iran’s compliance, as well as understanding of where Iran currently stands with respect to knowledge of nuclear weapons design.

One such side deal was recently revealed by the Associated Press, showing that Iran itself would be tasked with collecting photographs and videos of the Parchin nuclear base, as well as obtaining soil samples from the site and providing equipment for “technical verification” by the IAEA.

On Friday, Fox News quoted California Representative Ed Royce as saying, “The agreement looks like Iran calls the shots, vetoing technical inspections when they want, where they want at the Parchin military site.” Critics are quick to tie this to their assessment of concessions provided to Iran by the P5+1, including provisions of the JCPOA that give Iran up to 24 days’ advance notice of inspections at sites that come under suspicion after implementation of the deal.

Notwithstanding these criticisms, more Democratic members of Congress joined Obama’s side in the past week. The USA Today reports that Nadler himself endorsed the deal following receipt of the letter, suggesting that he may have been swayed by its assurances, which declared in part that the US has “a wide range of unilateral and multilateral responses that [it] can employ should Iran fail to meet its commitments.”

A large portion of the letter was also committed to discussing the US role in securing the safety of its primary Middle Eastern ally, Israel, in the new context of the JCPOA. This focus is surely indicative of the major role of the pro-Israel lobby in helping to maintain unanimous Republican opposition to the deal, as well as in poaching Democratic votes for a resolution of disapproval.

Many pro-Israel groups, as well as Israeli Prime Minister Benjamin Netanyahu, have made it clear that they consider the Iran nuclear deal to amplify an existential threat to the Jewish state, not only because they believe it fails to prevent Iran’s progress toward a nuclear weapon but also because sanctions relief and engagement with the world community may help Iran to expand its intrusions into the broader Middle East.

This point was newly emphasized after a series of rockets were fired into Israel from Syria on Thursday, prompting a massive response from Israeli Defense Forces. The Times of Israel reported on Friday that a senior Israeli security official blamed Iran for the latest attacks. This comes close on the heels of earlier remarks from Israeli officials noting that Iran has been behind every attack on Israel originating in the Golan Heights in roughly the past two years.

The senior security official named Saeed Izadi, the head of the Palestinian division of the Iranian Revolutionary Guards’ Quds Force, as the planner of the attack, which was reportedly carried out by Palestinian Islamic Jihad.

The Iranian-controlled Lebanese paramilitary Hezbollah has also developed a seemingly permanent presence in Syria, where Islamic Jihad is based and Iran has been conducting extensive operation in support of embattled President Bashar al-Assad. This growing Iranian presence and proxy influence in Syria partly explains Israeli Defense Minister Moshe Ya’alon’s claim that Thursday’s rocket attacks are merely a “coming attraction” for future attacks originating in Iran.

Ya’alon joined other critics of the Iran nuclear deal in saying that it would directly result in Iran increasing its funding for terrorist groups, including those operating on Israel’s border.

Arutz Sheva reports that Netanyahu responded to the rocket attacks in a statement on Friday. “This is further clear indication of Iran’s increasing involvement in attacks against Israel in particular and against regional targets in general,” he said. “The ink on the nuclear agreement has not yet dried, and this attack shows clearly how Iran plans to act the moment after the international sanctions are removed.”

Iran’s intentions not only toward Israel but also toward all Western assets and interests in the region, were also telegraphed by Iranian Defense Minister Hossein Dehqan on Friday. According to Iran’s state-affiliated Tasnim News Agency, Dehqan told a gathering of worshippers in Tehran that none of Iran’s military ambitions would be slowed by the JCPOA or by any other agreement. The Revolutionary Guards Brigadier General went on to present this commitment to military growth as a threat to “enemies” in the West.

“The enemies should know that if they seek to take action against the Islamic Republic of Iran, they will face a crushing response that would make them regret,” Dehqan said.

While President Obama’s letter speaks of willingness to confront Iran on its aggressive activities, he has also repeatedly referred to his belief that the nuclear agreement may encourage Iran to moderate internally – a notion that has been categorically rejected by opponents of the Iranian regime such as the National Council of Resistance of Iran.

On Thursday, The Guardian pointed to recent, unsubstantiated accusations of spying against a Wall Street Journal reporter as indicative of a larger pattern of attacks against Western journalists, officials, and activists. As an example of unchanged establishment attitudes toward such figures, The Guardian mentions a new round of propaganda directed against Ahmad Shaheed, the UN special rapporteur for human rights in Iran.

To this one might add Jason Rezaian, the Washington Post correspondent who was arrested in July of last year and who is currently awaiting a judgement on accusations of national security crimes. Many critics of the Obama administration’s Iran policy have suggested that his arrest was aimed at securing greater leverage in the nuclear negotiations, and thus at securing some of the much-maligned concessions that have motivated staunch opposition to the deal in the US Congress.