Following talks in Ramallah with Palestinian Prime Minister Rami Hamdallah (pictured, right) on Tuesday and with Israeli leaders the previous day, Guterres (pictured, left) expressed his "total commitment" to a two-state solution to end decades of conflict between Israelis and Palestinians.
"There is no plan B to a two-state solution," he said, calling it the only way to guarantee that peace would be established.
He added that settlement activity by Israelis in the occupied West Bank was illegal under international law and a "major obstacle" to resolving the conflict.
The plan for an independent Palestinian state alongside Israel has been the basis of international diplomacy for decades. The Palestinians want all of the West Bank, as well as east Jerusalem and the Gaza strip for their future state. Israel captured the territories in 1967, but withdrew from Gaza in 2005. But the concept of a two-state solution has recently been cast into doubt by both Israel's government and the White House.
Netanyahu doubles down on settlements
Guterres's remarks came the day after he met Israeli Prime Minister Benjamin Netanyahu, who late Monday evening vowed not to remove any settlements from the West Bank.
"We have returned here for good," he told the audience at a ceremony in the settlement of Barkan. "There will be no more uprooting of settlements."
"It's been proven that it doesn't help peace. We uprooted settlements and what did we get? We got rockets," he said, referring to the conflicts which followed the Israeli withdrawal from Gaza.
White House position unclear
Peace negotiations between Israel and the Palestinians have been at a standstill since a US-led peace initiative collapsed in 2014.
New US President Donald Trump has said he wanted to reach what he calls "the ultimate deal" but has himself cast doubt on support for a two-state solution, saying he could endorse a single state if that meant peace - a contrast to longstanding US policy.
A US delegation led by White House advisor and Trump's son-in-law, Jared Kushner, held talks with Netanyahu and Palestinian President Mahmoud Abbas, as well as other Middle East leaders, last week.
On Tuesday, Palestinian Prime Minister Rami Hamdallah said they were waiting for the US to formulate a clear approach - and for their position on the questions of settlements and the two-state solution.
"So far, the US administration has not responded to these two questions, and promised they will be back in the next few weeks with clarifications and a work plan for the next phase," Hamdallah said.
As well as criticizing settlements, during his visit, Guterres also called on Palestinian leaders to condemn "terrorism."
"It is important to create conditions for leaders of all sides to appeal for calm, to avoid forms of incitement, for violence to settle down," he said.
se/kms (AFP, AP, dpa)