US Secretary of State John Kerry visited Jordan on Friday for talks with King Abdullah II on the Israeli-Palestinian peace process, a US spokeswoman said.
The brief stop in the Red Sea port of Aqaba, where the talks were held, was not previously announced.
State Department spokeswoman Marie Harf said Kerry, who arrived from Rome from where he also brought back his Jordanian counterpart Nasser Judeh, would discuss the Middle East peace process with the monarch.
"We are arriving in Aqaba, Jordan, with Foreign Minister Judeh today to see King Abdullah to talk about the peace process," Harf said.
Jordan is one of only two Arab states to have signed a peace treaty with Israel, and King Abdullah holds a special position because the 1994 accord recognises his country's "historic" role in caring for Muslim holy sites in east Jerusalem.
Last month, Jordan warned that it might review the peace treaty after Israeli MPs began a debate on allowing Jewish prayers at Jerusalem's sensitive Al-Aqsa mosque compound, saying the kingdom's custodianship was "not a privilege granted by Israel".
Israel and the Palestinians remained deadlocked in ongoing peace talks that Kerry helped to launch last July.
Prime Minister Benjamin Netanyahu on Tuesday urged Palestinian president Mahmud Abbas to recognise Israel as a Jewish state and to "abandon the fantasy" of flooding it with returning Palestinian refugees.
His remarks sparked a furious reaction from the Palestinians, who denounced his demand and said it had effectively put the final nail in the coffin of the talks.
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- Kerry's Herculean task -
The spat threw a harsh spotlight on the divide between the two sides and the Herculean task faced by Kerry, who is trying to get them to agree on a framework for extending direct peace talks beyond an April 29 deadline.
Israel has repeatedly insisted there will be no peace deal without addressing the issue of recognition, and a clause relating to this has been inserted into Kerry's as-yet-unpublished framework proposal.
For the Palestinians, the issue is intimately entwined with the fate of their refugees who were forced out of their homes or fled in 1948 when Israel became a state.
They see Netanyahu's demand as a way of sidestepping a negotiated solution to the refugee issue.
The Palestinians have also long viewed Israeli settlement construction as a major obstacle to peace talks, arguing Israel is actively building on land that should be part of their future state.
Netanyahu has also alluded to Israel's demand to retain a military presence along the Jordan Valley, which runs down the eastern flank of the West Bank, in any future deal, saying he would not cede security to foreign peacekeepers.
Kerry has said a peace treaty will deal with all the core issues dividing the two sides, including the contours of a future Palestinian state, refugees, the fate of Jerusalem claimed by both as a capital, security and mutual recognition.
Under the US proposal, a unified Jerusalem would be the capital of both states without defining the outlines of east Jerusalem.