Dozens of U.S. officials have called on the Obama administration to order “targeted military strikes” against the regime of Bashar al-Assad in Syria, with the aim of pressuring Damascus to accept a binding cease-fire and engage in peace talks.

The Wall Street Journal reported that 51 State Department officials advising Syria policy signed the so-called “dissent channel cable”.

State Department spokesman John Kirby confirmed the cable’s existence Thursday, but said he would not comment further until officials have reviewed its contents.

The cable expresses clear frustration with America‘s inability to halt a civil war that has killed perhaps a half-million people and contributed to a worldwide refugee crisis, and goes to the heart of Obama’s reluctance to enter the fray.