The announcement comes amid speculation the N.D. senator could run for governor in 2016.
Booker is the 35th senator to back the deal.
Warren declined to say whether she discussed a joint 2016 presidential ticket with the vice president.
The secretary says administration will work on regional security following Iran deal.
Jordain Carney 09/02/15 10:26 AM EDT
The Maryland Democrat's support all but ensures the agreement will survive in the Senate.
Coons said Biden deserves the "time and the space" to make a decision on whether to run.
The President is one vote away from securing a major foreign policy goal.
Julian Hattem 09/01/15 01:37 PM EDT
Democrats are now just two votes away from upholding Obama's veto.
The top Dem on the Foreign Relations panel said he will announce his decision "soon."
Julian Hattem 08/31/15 03:58 PM EDT
Tom Cotton, a leading opponent of the Iran deal, is on a weeklong trip to Israel.