U.S. Secretary of State John Kerry will unexpectedly travel to Geneva on Friday afternoon to meet with Iran’s Foreign Minister Javad Zarif, NBC News reports.

Nuclear talks between Iran and the so-called P5+1 nations resumed in Geneva Thursday morning.

Word of Kerry’s impending arrival is the strongest sign so far of an agreement on a first step toward a comprehensive final deal, according to NBC.

Earlier, a senior American official and Zarif both said a deal could be reached Friday.

The United States was pressuring Iran to halt its nuclear program in return for a limited and reversible reprieve on economic sanctions.

According to one report in the British Telegraph, the U.S. was planning to propose a short-term nuclear agreement with Iran which would allow Tehran to continue enriching uranium at low levels.

Earlier reports indicated that the West was planning to offer Iran a cash windfall from its frozen oil revenues, allowing Tehran to unlock some of the money held under the crippling sanctions in exchange for it agreeing to halt all nuclear activity while more detailed negotiations continued.

Responding to the reports of a possible breakthrough with Iran, Prime Minister Binyamin Netanyahu warned Thursday evening that signing an interim deal with Iran would be a mistake of “historic proportions,” but that appears to be precisely the deal being hammered out.

On Wednesday, Israeli officials had warned against a compromise that would allow Iran to reduce its nuclear capability in exchange for a reduction in sanctions.