U.S. Defense Secretary Chuck Hagel says allies need to remain "closer than ever" as challenges in the Middle East become more complicated.
Hagel made the remark Tuesday as he met with Israeli Prime Minister Benjamin Netanyahu on the last day of a three-day visit to Israel.
Hagel said that working together the two countries could make the Middle East better and more secure in "a difficult and dangerous time."
Mr. Netanyahu said Israel appreciates U.S. military and security support, and said Israel "cannot accept" the arming of terrorist groups by Iran, nor what he said is that country's pursuit of nuclear weapons.
Hagel earlier said the U.S. government supports Israel but disagrees on the timing of a possible Israeli military strike against Iran.
Iran says its nuclear program is strictly for peaceful purposes.
Israel was the first stop on Hagel's five-nation tour of the Middle East. It came as the U.S. government announced it would permit the sale of $10 billion worth of advanced U.S. weapons to Israel, Saudi Arabia and the United Arab Emirates.
As the two leaders were meeting in Jerusalem on Tuesday, a senior Israeli officer told a security conference in Tel Aviv that Israel has evidence that the Syrian government is using chemical weapons against Syrian rebels.
The head of the Israeli army's military intelligence division, Brigadier-General Itai Brun, said photos of victims taken in Syria showed signs that they had died of poisoning from a nerve gas that he said most likely was Sarin.
Israel and the United States are worried that stockpiles of Syrian chemical weapons could fall into the hands of extremists as rebels advance in their battle to overthrow the Syrian government.
Both governments have said using such weapons could bring international intervention.
Hagel was asked about such reports Monday but said the U.S. did not yet have conclusive evidence of chemical weapons use by the Syrian government.