US President Barack Obama said Wednesday that critics of the deal signed between world powers and Iran, such as Prime Minister Benjamin Netanyahu and Republican lawmakers, have failed to offer a better alternative to the agreement.

Obama made the comments at a White House press conference in which he defended the deal signed Tuesday between Iran and the P5+1 group of world powers made up of the US, Britain, France, Russia, China and Germany.

"Israel has legitimate concerns about their security relative to Iran. It is a large country, with a sizable military that has proclaimed Israel shouldn't exist, denied the Holocaust and funded Hezbollah which has missiles pointed at Tel Aviv," Obama said.

However, all those threats would be compounded if Iran were able to obtain nuclear weapons, and the deal reached with Tehran represents the best path toward preventing that from occurring, he argued.

"For all of Netanyahu's and the Republicans' objections, none of them have presented to me, or to the American people, an alternative," Obama charged.

"I hear the talking points that this is a historically bad deal that will threaten Israel, the world and the US. What I haven't heard is: What is your alternative?" he asked.

"The issue is either resolved diplomatically through negotiations or through force, through war," Obama posited. "Those are the options," he said.

Obama dismissed critics who say that a better deal should have been sought in which Iran has no nuclear capacity at all, peaceful or otherwise, holding that Iran would never have accepted such an agreement.

The US president said that the deal cuts off all of Iran's pathways to a nuclear weapons program, and without a deal, those pathways remain open.

"This deal makes our country and the world safer and more secure," Obama said, adding that "the alternative would endanger our security, that's the choice we face."

"Future generations will judge us harshly if we let this opportunity slip away," Obama added.

"This deal is our best means of assuring Iran doesn't get a nuclear weapon. This is an opportunity that may not come again in our lifetimes," he said.

Obama said that despite the deal, Washington would still disagree with Iran's support for terrorism and its support for proxies such as Hezbollah.

He said that he hoped the deal would spur Iran to act in a less hostile manner, but that the US was not building on such a course of actions.

The deal will make it easier for the West to check up on Iran's "nefarious activities," he claimed.

"We are not normalizing diplomatic relations with Iran. We will try to encourage them to take a more constructive role in the region, but we're not betting on it," he said.

"The deal won't solve all those other problems, but if that's the argument against the deal, it defies logic, it makes no sense," he said, adding that the deal was meant solely to prevent Iran from obtaining a nuclear weapon.

Obama said that he was not concerned about the spin being put on the deal by hardliners in Tehran or Syrian dictator Bashar Assad who have touted the deal as a victory for Iran. "That's what politicians do," he said.