WASHINGTON -- After sparking a furor in Washington Monday with a letter signed by fellow Republican senators warning Iran against nuclear diplomacy with the Obama administration, Sen. Tom Cotton (R-Ark.) went to the extra trouble of having his message translated into Farsi for Iranian leaders. Among his targets: foreign minister Mohammad Javad Zarif.

Cotton needn't have bothered with the translation. Zarif is more than capable of reading the Republicans' letter in English. He attended prep school in San Francisco, San Francisco State University, Columbia University, and the University of Denver's School of International Studies (where, Zarif told The New Yorker's Robin Wright, a professor who had taught GOP foreign policy icon Condoleezza Rice once quipped to the young Iranian, "In Denver, we produce liberals like Javad Zarif, not conservatives like Condi Rice.")

Zarif, leading his nation's negotiations with the U.S., the U.K., France, Germany, Russia and China, put that education to use in his response Monday to the Republican message, which suggested that Iran's leaders "may not fully understand our constitutional system."

Zarif answered that it was Cotton and the 46 other Republican senators who signed his letter who suffered from a lack of "understanding."

"The authors may not fully understand that in international law, governments represent the entirety of their respective states, are responsible for the conduct of foreign affairs, are required to fulfil the obligations they undertake with other states and may not invoke their internal law as justification for failure to perform their international obligations," Zarif said, according to Iran's government-controlled Tasnim News Agency.

He suggested that the Republican warning that a successor to President Barack Obama could undo any agreement with Iran was baseless. Zarif said the "change of administration does not in any way relieve the next administration from international obligations undertaken by its predecessor."

Any agreement to limit Iran's nuclear program in exchange for sanctions relief would likely be endorsed by the United Nations Security Council, Zarif said, as well as the other nations involved in the talks. A State Department official told The Huffington Post in an email that any potential deal with Iran would be a non-binding international agreement -- not the kind of pact Cotton and the GOP senators referenced in their letter.

Zarif noted, as did the State Department official, that many U.S. international agreements, including those that protect the rights of U.S. troops based abroad, are not ratified by the Senate. To the Zarif, that means that even if the deal with his country is not an executive agreement the way Cotton and his GOP colleagues suggested, the senators have undermined other U.S. agreements by suggesting they aren't taken seriously.

Zarif on Monday went even further by using the GOP misstep to seize an advantage that the Obama administration has said it does not want to give Iran: the chance to say the nuclear negotiations could fail because of the U.S.

"The Islamic Republic of Iran has entered these negotiations in good faith and with the political will to reach an agreement," Zarif said. "It is imperative for our counterparts to prove similar good faith and political will in order to make an agreement possible.”

As chief nuclear negotiator, Zarif has been in a precarious position as the talks, twice extended, continue. He has been slammed by Iran's hard-liners, most recently over a photo op with Secretary of State John Kerry in Geneva in mid-January. That Zarif went for a stroll with Kerry was, according to one influential paramilitary commander in Iran, akin to “trampling on the blood of martyrs."

Monday's letter presented Zarif with a rare opportunity to both look tough on the U.S. for his domestic audience and reasonable to the international community.

It was Cotton who drew flak. The State Department official who emailed The Huffington Post called Cotton's stunt "profoundly contrary to U.S. interests." Obama told reporters he saw the GOP effort as an example of "some members of Congress wanting to make common cause with the hardliners in Iran."

"It's an unusual coalition," the president added.

Neither those comments nor the statements from Zarif seemed to sway Cotton. Appearing on CNN in the late afternoon, the freshman senator told Jake Tapper he simply did not believe there was such a thing as an Iranian leadership that could be negotiated with -- begging the question of why he made such a high-profile and controversial appeal to Tehran in the first place.

"Jake, they're nothing but hard-liners in Iran," Cotton said. "Nothing but hard-line Islamic extremists who have been killing Americans around the world for 35 years."

The Obama administration maintains that diplomacy is the only way to prevent Iran from pursuing nuclear weapons. The administration also has made clear it will pursue any option to prevent Iran from gaining a nuclear weapon, though it would like to accomplish that through peaceful talks rather than military action.