A group of former US diplomats has sent a letter to Congress, urging members of both chambers not to reject the nuclear agreement with Iran.

The letter, signed by former undersecretaries of state and five former American ambassadors to Israel, says the July 14 accord “will leave Iran no legitimate avenue to produce a nuclear weapon during the next 10 to 15 years.”

Israel and its allies in Congress accuse Iran of pursuing a nuclear weapon. Tehran strongly rejects the allegation, saying its nuclear program is entirely peaceful.

The White House has launched an aggressive campaign on Capitol Hill in an effort to sell the Iran agreement to congressional skeptics, who have until September 17 to review and potentially vote down the accord.

US Secretary of Energy Ernest Moniz speaks while US Secretary of State John Kerry listens during a hearing of the Senate Foreign Relations Committee on the Iran nuclear agreement on July 23, 2015. (AFP photo)

The letter, sent out separately to the House and Senate on Monday, says the international agreement “does meet all of the key goals required for high confidence” that it would not be violated by Iran.

Senior Republicans in Congress have vowed to do their best effort to scuttle the Joint Comprehensive Plan of Action, which they say will threaten Israel and empower Iran.

Monday’s letter, however, cautions the critics that without the accord, “the risks will be much higher for the United States and Israel.”

“Those who advocate rejection of the JCPOA should assess carefully the value and feasibility of any alternative strategy to meet the goal of better protecting the security of the US and Israel,” it states.

On Monday, President Barack Obama chastised Republican critics of the nuclear agreement.

Obama blasts Republican critics of the nuclear agreement with Iran during a joint press conference in Addis Ababa on July 27, 2015. (AFP photo)

At a news conference in Ethiopia, he accused the GOP presidential candidates of playing “fast and loose” with the facts to kill the accord.

Obama has vowed to veto any congressional resolution seeking to reject the nuclear agreement.