(CNN) — More than 50 State Department officials signed an internal memo protesting U.S. policy in Syria, calling for targeted U.S. military strikes against the regime of Bashar al-Assad and urging regime change as the only way to defeat ISIS.

The cable says that U.S. policy in the Middle East has been "overwhelmed" by the continuing violence in Syria. It calls for a "judicious use of stand-off and air weapons, which would undergird and drive a more focused and hard-nosed U.S.-led diplomatic process."

CNN reviewed a draft of the memo, which has since been classified. The Wall Street Journalfirst reported on the memo's existence.

The internal memo was sent throughout the "dissent channel," a mechanism for State Department officials to offer alternative views on foreign policy without freedom of retaliation or retaliation. It was established in the 1960s during the Vietnam War to ensure that senior leadership in the department would have access to alternative policy views on the war.

The 51 officials who signed the memo are mostly from the rank and file of the department, many of them career officers in the foreign service who have been involved in Syria policy over the past several years either in Washington or overseas.

There are no high-level names but they reflect a widespread view in the State Department that tougher military action in Syria is needed to force Assad to negotiate a diplomatic solution. Secretary of State John Kerry himself has advocated a more muscular U.S. military posture in Syria to force Assad to negotiate a political settlement.

Memo: Tougher military action needed in Syria

Sources familiar with the memo said the officials had been discussing sending it for some time, but they finally decided to move forward because negotiations with Russia over a political transition in Syria have all but collapsed and the fragile ceasefire continues to disintegrate. The memo says that neither Assad nor Russia have taken past ceasefires and negotiations seriously and suggests a more robust military approach was needed to force a transitional government in Syria.

President Barack Obama has resisted wading deeper into the Syria conflict, but officials familiar with the memo said the State Department officials could be trying to force a policy debate in the upcoming elections. Hillary Clinton has promised a tougher policy toward Assad, while Donald Trump has promised to get tough on ISIS but would work with Russia.

News of the cable came as Pentagon officials said Russia launched airstrikes against U.S.-backed Syrian rebels in southern Syria. Earlier Thursday, Russia said it wanted a long term ceasefire in the northern city of Aleppo. Russia has been providing military support to the Syrian army.

The memo calls on the U.S. to create a stronger partnership with moderate rebel forces to battle both Assad's forces and ISIS, which would change the tide of the conflict against the regime and "increase the chances for peace by sending a clear signal to the regime and its backers that there will be no military solution to the conflict."

It also warns that as the regime "continues to bomb and starve" Syria's Sunni population, the U.S. will lose potential allies among Syria's Sunni population to fight ISIS. Moreover, it says, U.S. failure to stop the regime's abuses "undermines both morally and materially the unity of the anti-Daesh coalition" and "will only bolster the ideological appeal of groups such as Daesh, even as they endure tactical setbacks on the battlefield." Daesh is an Arabic acronym for ISIS.

State Department spokesman John Kirby confirmed the existence of the cable but would not go into detail about the contents. He said doing so would not be respectful of the process.

"We are aware of a dissent channel cable written by a group of State Department employees regarding the situation in Syria. We are reviewing the cable now, which came up very recently," he said. "This is an important vehicle that the secretary, as well as the department institutionally, values and respects."