WASHINGTON -- Fifty-one career diplomats from across the State Department have signed an internal cable calling for a new U.S. policy on Syria, including more direct action against Syrian dictator Bashar Assad, CBS News has learned.

The cable itself is classified. It was formally submitted this week to the State Department's Director of Policy Planning and signed by officials who handle several different areas, including human rights and the Middle East.

One of the officials responsible for the cable told CBS News it was written in response to five years of what the signatories consider to be a failed policy. They say Assad has not faced consequences for his actions, including bombing his own people and U.S.-backed rebel groups.

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Assad was also faulted in the cable for failing to allow humanitarian shipments of food and medicine to reach areas where Syrians have been starving to death, despite agreements negotiated by the U.S. and Russia.

The authors argued that while a political solution is needed in Syria, it is hard to have diplomatic leverage when there are no costs for abuse. According to the cable, the White House policy has been to ignore Assad while focusing on ISIS -- which the authors say is not a recipe for success. Assad's violence feeds ISIS, endangers U.S. allies, lead to a massive refugee crisis that is destabilizing Europe, and has mixed the threat of terrorism with human rights issue of refugees.

The cable does not make specific policy recommendations such as U.S. airstrikes but comes close, arguing that Assad's artillery and air power must be removed as threats to the U.S.-backed rebels.

The officials who spoke with CBS News said having 51 signatories on a cable unprecedented. By comparison, a dissent cable sent in 1993 objecting to President Bill Clinton's reluctance to stop ethnic cleansing in Bosnia was signed onto by a dozen State Department diplomats.

Many of the signatories of the Syria cable fear that its leak to the press, so soon after submission, will make the White House dismiss the criticism as a political matter and not consider the policy criticisms. According to the authors, it was not meant to air dirty laundry but rather to spark a policy review. All of the signatories are professional, career diplomats and not political appointees.

Multiple sources confirm that the Secretary of State John Kerry himself has privately recommended a more muscular U.S. role in Syria but has had numerous proposals shut down by the White House.

"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, and I am not going to comment on the contents," State Department spokesman John Kirby said in a statement Thursday night.

"The Dissent Channel is an existing official vehicle in place to allow State Department employees to convey alternative views and perspectives on policy issues," Kirby said. "This is an important vehicle that the Secretary, as well as the Department institutionally, values and respects that allows Department employees to express policy views candidly and privately to senior leadership."

Kirby said Kerry has been given a brief on the cable. Jon Finer, the Director of Policy Planning to whom the cable was sent, has 30 to 60 days to respond in writing, according to Kirby.