Sen. Bernie Sanders (I-Vt.) has blasted 47 Republicans in the U.S. Senate for sending a letter this week to Iranian leaders and said the incident goes to show that some of his colleagues are simply “itching for war” when it comes to Iran.

The open letter (pdf) in question—sent on Monday and addressed to the  “Leaders of the Islamic Republic of Iran”—warned that its signatories would “consider any agreement regarding your nuclear-weapons program that is not approved by the Congress as nothing more than an executive agreement” that could be jettisoned following the next congressional and presidential elections in 2016. Despite the rhetoric of the letter, there is no evidence showing Iran has an active nuclear weapons program and the nation’s leadership has repeatedly stated that it has no current ambitions for such a program.

Widely regarded as an unorthodox attempt to sabotage ongoing diplomatic efforts regarding Iran’s research and uranium enrichment program for its civilian nuclear program, Sanders was among those publicly criticizing the nature and content of the letter as well as the nearly 50 senators—including the top Republican leadership and presidential hopefuls—who signed it.

“[M]y Republican friends seem to be itching for that war,” Sanders told reporters on Tuesday following an event in Washington, D.C. “When you sabotage the effort to reach a peace agreement by the leader of the United States of America — the man who is charged with dealing with foreign policy — that, to me, is really unspeakable.”

Making reference to the disastrous and costly wars in both Iraq and Afghanistan, he added, “Apparently, some of my Republican colleagues do not believe that two wars are enough… I think that is a very, very tragic position to hold.” 

Sanders has made it clear he is considering running for president in 2016 as a progressive challenger to Hillary Clinton, the presumptive Democratic nominee.