US President Donald Trump began his visit to Israel by warning of the threat that Iran could pose if it were to develop nuclear weapons."Iran must never be allowed to possess a nuclear weapon," Trump said, standing beside Israeli President Reuven Rivlin.Donald Trump on Monday was on the second stop of his first international tour, having arrived from Riyadh, Saudi Arabia, aboard Air Force One, Efe news reported.The President reinforced the message when he went on to have a meeting with Israeli Prime Minister Benjamin Netanyahu.Trump also labeled the nuclear agreement reached between Iran and the Group 5 + 1 (the five permanent members of the UN Security Council plus Germany) as a mistake."It was a terrible, terrible thing for the United States to enter that deal and, believe me, Iran will never have a nuclear weapon, that I can tell you," Trump said to Netanyahu.Trump warned of Iran's escalating presence in the region."No matter where we go we see the signs of Iran in the Middle East," Trump said.