Washington, Paris and Cairo, AP/Asharq Al-Awsat—President Barack Obama launched an aggressive and detailed defense of a landmark Iranian nuclear accord, rejecting the idea that it leaves Tehran on the brink of a bomb and arguing the only alternative to the diplomatic deal is war.

The president vigorously challenged his critics during a lengthy White House news conference on Wednesday, a day after Iran, the US and five other world powers finalized a historic, years-long agreement to curb Tehran’s nuclear program in exchange for billions of dollars in sanctions relief. Opposition to the deal has been fierce, both in Washington and Israel. The Gulf states have also expressed concerns.

“Either the issue of Iran obtaining a nuclear weapon is resolved diplomatically through a negotiation or it’s resolved through force, through war,” Obama said. “Those are the options.”

Israeli Prime Minister Benjamin Netanyahu, perhaps the fiercest critic of Obama’s overtures to Iran, showed no sign he could be persuaded to even tolerate the agreement. In remarks to Israel’s parliament, Netanyahu said he was not bound by the terms of the deal and could still take military action against Iran. Netanyahu sees Iran’s suspected pursuit of a nuclear weapon as a threat to Israel’s existence.

In Congress, resistance comes not only from Republicans, but also Obama’s own Democratic Party. Vice President Joe Biden spent the morning on Capitol Hill meeting privately with House Democrats, and planned to return Thursday to make a similar pitch to Democrats on the Senate Foreign Relations Committee.

The president said he welcomed a “robust” debate with Congress, but showed little patience for what he cast as politically motivated opposition. Lawmakers can’t block the nuclear deal, but they can try to undermine it by insisting US sanctions stay in place.

In Tehran, Iranians took to the streets to celebrate the accord, and even Iran’s hardliners offered only mild criticism—a far cry from the outspoken opposition that the White House had feared.

The nuclear accord has become a centerpiece of Obama’s foreign policy, a high-stakes gamble that diplomatic engagement with a longtime American foe could resolve one of the world’s most pressing security challenges. The importance of the deal to Obama was evident Wednesday, both in his detailed knowledge of its technical provisions and his insistence that no critique go unanswered.

An hour into the East Room news conference, Obama asked if reporters had other questions about Iran—a highly unusual inquiry from a president who is rarely so freewheeling in his exchanges with the press. He pulled a piece of paper out of his pocket, saying he had “made notes” about the main criticisms of the deal and wanted to ensure each had been addressed.

The accord requires Iran to dismantle key elements of its nuclear program, lower its uranium enrichment levels, and give up thousands of centrifuges. International inspectors will have access to Iran’s declared nuclear facilities, but must request visits to Iran’s military sites, access that isn’t guaranteed. If Iran abides by the parameters, it will receive billions of dollars in relief from crippling international sanctions that have badly damaged the country’s economy.

The deal does nothing to address Iran’s broader support for terrorism in the Middle East or its detention of several American citizens, though some US officials hold out hope it could eventually lead Tehran to reassess its role in the world.

Obama, however, outlined a narrower ambition, saying the deal should be judged solely on whether it stops Iran from obtaining a nuclear weapon. As to whether the agreement might change Iran’s other behavior, he said, “We’re not betting on it.”

The president also sharply rebuffed a suggestion that he was content to let American detainees languish in Iran while he celebrated a deal. “That’s nonsense,” he said, adding that Iran would have taken advantage of any US effort to link the nuclear accord to the release of US citizens.

To those who argue sanctions relief will leave Iran flush with cash to fund terrorism, Obama said Tehran is already backing Hezbollah and other groups on the cheap. He noted that the Iranian government is under pressure from citizens to use any influx of international funds to improve the country’s struggling economy.

Obama insisted sanctions on Iran could be “snapped back” in place if Iran cheats on the deal, even if Russia and China object. He defended the 24-day window Iran would have before international inspectors gain access to suspicious sites, saying nuclear material “leaves a trace” and suggesting the US has other means of monitoring facilities.

Meanwhile on Wednesday Saudi Arabia’s King Salman Bin Abdulaziz said the Kingdom supported the deal so long as it prevented Iran from obtaining nuclear weapons and ensured all nuclear sites were inspected thoroughly.

Obama, for his part, said the US was willing to work with its Gulf allies to counter Iran’s regional ambitions and interference into the affairs of other countries in the Middle East.

Speaking to Asharq Al-Awsat on Wednesday, Maryam Rajavi, head of the National Council of Resistance of Iran, a coalition of Iranian opposition groups, expressed misgivings regarding the deal.

She said Tehran could still seek to bypass inspectors in order to obtain a nuclear weapon by secretive means. However, she also stressed concessions made during the negotiations had weakened the “religious fascist” Tehran regime, which she believed could also help increase opposition toward the regime domestically.

“Even though the deal won’t close the door on the Mullahs’ secret maneuvering in the hope of obtaining a nuclear weapon, it does however give a chance for mobilizing dissent inside Iran itself,” she said.