US Secretary of State John Kerry has warned Israeli Prime Minister Benjamin Netanyahu about planning to attack Iran’s nuclear facilities following the conclusion of nuclear negotiations.

He called a unilateral military action against Iran a “huge mistake.”

"That'd be an enormous mistake, a huge mistake with grave consequences for Israel and for the region, and I don't think it's necessary," Kerry told NBC News on Friday when asked about Tel Aviv’s possible strike.

Washington and its five negotiating partners concluded the nuclear negotiations with Iran in Vienna on July 14.

Iran sanctions are set to be removed in exchange for some limitations on the country’s nuclear energy program.

During a speech at the Council on Foreign Relations earlier on Friday, the top US diplomat also noted that Israel could be blamed for the rejection of the agreement by Congress.

"I fear that what could happen is if Congress were to overturn it, our friends Israel could actually wind up being more isolated and more blamed," he said.

Kerry also questioned Netanyahu's warning in 2012 that the Islamic Republic would have a nuclear weapons capability by the following year.

"We've seen the prime minister draw a cartoon of a bomb at the UN and so on and so forth," he said. "But what's happened? What has anyone done about it? Anybody got a plan to roll it back?"

Kerry also lashed out at critics of the agreement for putting pressure on the Obama administration to ratchet up sanctions against Iran.

"I've heard people say, 'Why don't you just ratchet up the sanctions?'" he said. "I'll tell you why -- because China, Russia, France and Germany and other countries don't think that's necessary if these guys are willing to negotiate and have a deal."

He also acknowledged that anti-Iran sanctions were not successful and warned about a military strike without the Vienna accord.

"We'd go right back to square one where we were with no alternatives. Iran is enriching, we have no inspections, we have no ability to know what they are doing, we don't roll back their program, we're back where we were and we are going to head to conflict," he said.

On Thursday, Kerry defended the outcome of the nuclear talks during a Senate hearing.