In an apparent reference to Israeli Prime Minister Benjamin Netanyahu, Kerry said on Tuesday, “Anybody running around right now, jumping in to say well we don’t like the deal, or this or that, doesn’t know what the deal is.”

Netanyahu and some other officials in his regime have accused the Obama administration of trying to strike a “bad deal” with Iran. 

“There is no deal yet,” Kerry told the US Senate Appropriations Committee. “And I caution people to wait and see what these negotiations produce.”

Iran and the P5+1 group of  states – Britain, France, China, Russia, the United States, Germany –  are holding negotiations to narrow remaining differences ahead of a deadline in late March for a framework agreement between the two sides. The deadline for the final agreement is July 1.

The scale of Iran’s uranium enrichment and the timetable for the lifting of anti-Iran sanctions are seen as major sticking points in the talks.

Kerry said the P5+1 group "had made inroads" since reaching an interim agreement with Iran in November 2013 on the Iranian nuclear issue. "We've gained unprecedented insight into it.”

The top US diplomat, however, sounded a note of caution, saying he was not sure yet whether a comprehensive agreement on Iran’s nuclear program was within reach. "And we expect to know soon whether or not Iran is willing to put together an acceptable, verifiable plan."