WASHINGTON >> President Barack Obama vigorously defended the nuclear deal with Iran on Wednesday, casting the historic accord as the only possibility to avert a war with Iran and a nuclear arms race in the Middle East.

A day after the U.S., Iran and world powers announced the deal, Obama said the U.S. faces a "fundamental choice" — whether or not to embrace the opportunity to resolve the Iranian nuclear issue peacefully. His remarks in a White House news conference appeared aimed squarely at Congress, where lawmakers are discussing legislation to try to stop the deal’s implementation.

"I expect the debate to be robust, and that’s how it should be," Obama said, imploring lawmakers who are skeptical of the deal to "remember the alternative."

Yet critics of the deal — including Israeli Prime Minister Benjamin Netanyahu — were only growing more outspoken. Addressing his country’s parliament on Wednesday, Netanyahu insisted Israel was not bound by the agreement, suggesting Israel could still take military action against Iran’s nuclear program even if the deal proceeds.

"We will reserve our right to defend ourselves against all of our enemies," Netanyahu said. "We have strength, and it is great and mighty."

Under the deal announced Tuesday, Iran’s nuclear program will be scaled back and closely monitored as the U.S. and world powers seek to cut off Iran’s ability to develop a nuclear weapon. In exchange, Iran will see biting economic sanctions eventually lifted, freeing up billions of dollars in oil revenue and frozen assets.

Obama, taking questions from reporters in the East Room, said that in the absence of a deal, the international economic sanctions that brought Iran to the negotiating table will unravel, and the world community will be unable to put the sanctions regime together.

"Without a deal, we risk even more war in the Middle East, and other countries in the Middle East would feel compelled to develop their own nuclear weapons," Obama said, adding that such a chain of events would risk a nuclear arms race "in the most dangerous region in the world."

As Obama defended the deal, his allies were mounting a concerted push to sell the agreement to skeptics, while the deal’s critics warned of dire consequences.

Vice President Joe Biden spent the morning on Capitol Hill briefing House Democrats, and told reporters he was confident that lawmakers would get behind the deal. Yet in Jerusalem, Israeli leaders were planning what is expected to be a lobbying effort in the U.S. Congress ahead of a review of the deal, starting with a visit to the U.S. by Netanyahu’s political rival, Isaac Herzog.

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

Opponents of the deal, including Israel, have lambasted the Obama administration for granting sanctions relief to Iran while it continues to fund terrorist groups in places like Syria, Yemen and Lebanon. Obama said the U.S. would keep trying to gain Tehran’s cooperation on other security issues, but acknowledged the Islamic republic might not change its behavior.

"We’re not betting on it," he said.

Aiming to frame the parameters for the growing debate, Obama bemoaned that his political opponents have wielded "speculation or misinformation" about the deal. While he said he hoped Congress would approve the deal based on the facts, he conceded that "we live in Washington, and politics do intrude."

"I am not betting on the Republican Party rallying behind this agreement," Obama said.

With a cornerstone of his foreign policy legacy on the line, Obama sought to rebut specific critiques that have been lobbed at the deal — such as concerns about whether sanctions can really be "snapped back" into place if Iran cheats. Obama insisted that they could, even if Russia or China object.

He rejected concerns that Iran could use procedural delays to stop inspectors from examining suspicious military sites until it was too late by arguing the world would have a full year to intervene before Iran could feasibly put together a bomb.

Although a longstanding embargo on selling arms to Iran will sunset in five years, Obama shrugged off that concern, too. He said the U.S. and its partners have other ways to prevent Iran from sending weapons to militant groups to spread chaos in the Middle East.