The United States says economic sanctions on Iran would be gradually phased out if a final nuclear agreement is reached between Tehran and six world powers before the June 30 deadline.
White House spokesman Josh Earnest said on April 6 that Washington was clear with Iranian officials in its demand that sanctions on Tehran would be lifted in different phases under a final deal.
He said those details are still to be negotiated.
Iranian officials have suggested since a framework deal curbing Iran's controversial nuclear program was agreed on April 2 that the U.S., EU, and United Nations sanctions against Iran would be lifted in full once a final deal is signed.
Earnest said it has "never" been the U.S. position that "all sanctions against Iran should be removed from day one."
Also on April 6, U.S. President Barack Obama rejected the idea that Iranian recognition of Israel's right to exist would be included in a final nuclear agreement.
Obama said in an interview with National Public Radio that such a demand, made by Israeli Prime Minister Benjamin Netanyahu on April 4, "is really akin to saying that we won't sign a deal unless the nature of the Iranian regime completely transforms."
Obama has said Israel has a right to be concerned about Iran's nuclear program, but the president said the U.S. will ensure any final nuclear deal with Iran maintains Israel's "qualitative military edge."
He added that Washington's "defense of Israel is unshakeable."
But Netanyahu denounced the framework understanding as a "bad deal."
Israeli Intelligence Minister Yuval Steinitz said on April 6 that if Iran "will produce nuclear weapons, this is an existential threat to Israel."
Steinitz added that in upcoming negotiations to finalize a deal with Iran officials from Britain, France, Germany, Russia, the United States, and China should insist on a complete stop of research and development on new centrifuges, a cut in the number of existing centrifuges, and a shutdown of a facility at Fordo used for enriching uranium.
He said Tehran should also agree to spot checks on its nuclear program "anywhere, anytime."
Steinitz said such terms would make a nuclear deal "a more reasonable agreement."
He said the current framework on "key parameters" of a deal shows it to be "dangerous...for Israel, the region, and the entire world."
Steinitz said Israel prefers a diplomatic solution to the issue but reserves the right to take military action against Iran, something he said is "going to remain on the table."
Meanwhile, key Democratic Senator Chuck Schumer said on April 6 that he supports a Republican proposal that would allow Congress to reject an Iran nuclear deal.
Based on reporting by Reuters and AP