He also visited his great-grandmother Princess Alice's tomb in the Russian Orthodox Church.
After that, he visited the Al-Buraq Wall (referred to by Jews as the "Western Wall"), where he prayed before moving on to the Church of the Holy Sepulcher.
On Thursday morning, the prince visited the historic Mount of Olives overlooking Jerusalem's Old City.
Accompanied by the Rabbi of the Wall, Shmuel Rabinowitz, and the Chief Rabbi of the United Kingdom and Commonwealth Ephraim Mirvis, the Prince signed the guestbook, writing "May the God of peace bless this region and all the world with peace".
Israel Hayom also pointed out that Kushner and Greenblatt have said in private conversations that they are planning to revise the plan in light of their recent visit.
Separately, he wrote in the Western Wall's official guest book: "May the God of peace bless this region and all the world with peace".
William is on the final day of his tour of Israel and the Palestinian Territories, the first official visit by a senior member of the British royal family to the areas.More news: Duckworth doesn't join Dem colleagues in calls to abolish ICE
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A devout Christian, she died in London in 1969 and had asked to be buried in Jerusalem, next to her aunt, who like Alice had become a nun and founded a convent.
Prince William was welcomed in Jordan by Crown Prince Hussein, 23, who will be his host throughout the two-day stay in the country, last Sunday.
Palestinian sources in Ramallah said Fatah has instructed its loyalists in the West Bank to play an active role in the campaign against the Trump plan.
William continued to the nearby Jalazoun refugee camp, where he met with Palestinian youths, ate hummus and other local dishes and visited a school and a clinic.
According to al-Ayyam, Israeli forces injured a Palestinian young man with a live round during a raid that triggered clashes in al-Khader town, south of Bethlehem. The Palestinians, he added, see the Trump plan as "ideas coming from [Prime Minister Benjamin] Netanyahu".
In the document, the British government expressed its support for "a national home for the Jewish people" in Palestine.
In his speech, the Duke of Cambridge told Palestinians: "My message tonight is that you have not been forgotten ..." Israeli forces also detained three Palestinians from the Tubas district, PPS identified them as Muhammad Ammar Daraghmeh, Usayd Saleh and Fares Maslamani.
"Until we meet again, Prince Charming", the British Embassy tweeted in Hebrew as William's plane taxied for departure from Tel Aviv's Ben-Gurion airport.