(JNS.org) Ten Democratic U.S. senators who support the Iran Nuclear Weapon Free Act of 2015, a new Iran sanctions bill initiated by Sens. Robert Menendez (D-NJ) and Mark Kirk (R-IL), told President Barack Obama that they would not vote for the sanctions until the deadline for a “political framework agreement” between Iran and the P5+1 powers on March 24.

The senators, including Menendez, wrote in a letter to Obama, “After March 24, we will only vote for this legislation on the Senate floor if Iran fails to reach agreement on a political framework that addresses all parameters of a comprehensive agreement. This deadline is the critical test of Iranian intentions.”

The senators also wrote that they “remain deeply skeptical that Iran is committed to making the concessions required to demonstrate to the world that its nuclear program is exclusively peaceful” by the March 24 deadline. The deadline for a final nuclear deal is June 30. Obama has vowed to veto any new Iran sanctions bill.

Last week, Menendez struck a harsher tone on the issue, saying that the Obama administration’s talking points on Iran sound like they come “straight out of Tehran.”