Iranian women carry photographs of relatives killed in the war Sunday. Negotiators have come to a cease-fire agreement between the United States and Iran, but President Donald Trump and Iranian leadership haven't yet approved it. Photo by Behnam Tofighi/UPI | License Photo

May 28 (UPI) -- A tentative cease-fire has been reached Thursday between the United States and Iran, but it still must be approved by the leadership of both countries.

The two sides agreed on a 60-day memorandum of understanding to keep the cease-fire that's been in place since early April and reopen the Strait of Hormuz, according to The Hill, the BBC and CNN.

The MOU also commits to negotiating on Iran's nuclear enrichment program and U.S. sanctions against Iran. The Iranian side agreed to not impose tolls on commercial ships in the strait and will begin removing mines from the vital shipping channel.

Sources told CNN that the most difficult issues with Iran's nuclear program still must be worked out as part of those negotiations.