Rep. Jared Polis took to his personal twitter account Tuesday to label a Republican senator "Tehran Tom" for his role in a letter sent to Iran.

The Colorado Democrat was referring to Sen. Tom Cotton, R-Ark., who led an effort to send a letter — signed by 47 Republican senators — to Iran's government regarding nuclear negotiations between the two nations.

"Tehran Tom took his case directly to the Iranian government," the Colorado Democrat tweeted.

"Tehran Tom asks Iranian Revolutionary Guards for help in battle against US diplomats," he added.

The letter, which was criticized by Vice President Joe Biden as "beneath the dignity" of the Senate, warns Iran that Congress must ultimately approve any deal between the Obama administration and Iran.

Cotton responded to the vice president's criticisms Monday, saying on MSNBC that Biden "has been wrong about nearly every foreign policy and national security decision in the last 40 years."

Screenshot below: