The U.S. and Iran are reportedly on the brink of reaching a deal to end the Middle East war as early as Sunday, Washington’s top diplomat said, even as Tehran insisted any agreement would not curb its nuclear program.

Washington and Tehran have observed a cease-fire since April 8 while mediators push for a negotiated settlement, although Iran has imposed controls on Gulf shipping and the U.S. has blockaded Iran's ports.

On Sunday, during a visit to India, U.S. Secretary of State Marco Rubio told reporters: "I do think perhaps there is the possibility that in the next few hours the world will get some good news."

This came after U.S. President Donald Trump posted on social media that the deal "has been largely negotiated, subject to finalization between the United States of America, the Islamic Republic of Iran, and the various other Countries."

Rubio said the agreement would start a "process that can ultimately leave us where the president wants us to be, and that is a world that no longer has to fear or worry about an Iranian nuclear weapon."