President Shimon Peres met Saturday with visiting Republican senators John McCain, Lindsey Graham and John Barrasso in Jerusalem and expressed optimism about a peace agreement with the Palestinians.

The American lawmakers were visiting Israel on a tour of the region. Their stay coincided with US Secretary of State John Kerry’s return to the Mideast to broker peace efforts between Israel and the Palestinians.

“It’s a time of decisions. All decisions are tough but not to make a decision is a mistake,” Peres told the senators. “Secretary Kerry in investing significant time and effort and I believe that peace is possible despite the difficulties.”

Peres met with the senators while Kerry, on his 10th visit to the region in the past year, met with Palestinian leaders in Ramallah in a bid to form a framework agreement between Israel and the Palestinians. He returned to Jerusalem in the evening to meet with Prime Minister Benjamin Netanyahu for the third time since arriving on Thursday.

“Before peace with Egypt [in1979], people said it was impossible,” the 90-year-old president said. “With the Palestinians it’s complicated for them and for us. I have known President Abbas for many years and I believe he really wants peace.”

McCain told Peres that he and his colleagues have “room for guarded optimism” about the peace talks after having met with Prime Minister Benjamin Netanyahu, Palestinian Authority President Mahmoud Abbas and Kerry.

“It’s a very difficult process but we appreciate Secretary Kerry’s great efforts and we also see a willingness that hasn’t necessarily always been there in the past,” he added.

Peres said that terrorism is the greatest threat posed to the Arab world, and that halting Iranian support for international terrorism must be stopped.

“As well as what we have put before the Iranians we have to put two more issues – one is the development of long range missiles capable of carrying nuclear warheads, they don’t need nuclear missiles if they don’t want nuclear weapons. The second thing is stopping Iranian intervention in terror across the world; they are engaged, unfortunately, everywhere,” Peres said.