Republicans send letter in attempt to sabotage President Obama's negotiations with Iran. Can you say "treason?"

Courtesy of Bloomberg:  

A group of 47 Republican senators has written an open letter to Iran's leaders warning them that any nuclear deal they sign with President Barack Obama's administration won’t last after Obama leaves office. Organized by freshman Senator Tom Cotton and signed by the chamber's entire party leadership as well as potential 2016 presidential contenders Marco Rubio, Ted Cruz and Rand Paul, the letter is meant not just to discourage the Iranian regime from signing a deal but also to pressure the White House into giving Congress some authority over the process. 

“It has come to our attention while observing your nuclear negotiations with our government that you may not fully understand our constitutional system … Anything not approved by Congress is a mere executive agreement,” the senators wrote. “The next president could revoke such an executive agreement with the stroke of a pen and future Congresses could modify the terms of the agreement at any time.” 

Arms-control advocates and supporters of the negotiations argue that the next president and the next Congress will have a hard time changing or canceling any Iran deal -- -- which is reportedly near done -- especially if it is working reasonably well. 

Many inside the Republican caucus, however, hope that by pointing out the long-term fragility of a deal with no congressional approval -- something Supreme Leader Ayatollah Ali Khamenei has also noted -- the Iranian regime might be convinced to think twice. "Iran's ayatollahs need to know before agreeing to any nuclear deal that … any unilateral executive agreement is one they accept at their own peril,” Cotton told me.

Okay not to use hyperbole here, but how is this NOT treason?