The United States will not take Iran at its word over pledges of openness on a believed nuclear weapons programme, Secretary of State John Kerry said Thursday, after Israel threatened to act against Tehran.
"I assure (Prime Minister Benjamin) Netanyahu and the people of Israel that nothing that we do is going to be based on trust," the top US diplomat told reporters in Tokyo.
"This is going to be based on a series of steps to guarantee to all of us that we have certainty on what's happening."
Kerry, in Tokyo for talks on the US-Japan security alliance, was speaking after Netanyahu told a UN summit that Israel was ready to act alone to stop Iran from making a nuclear bomb.
"Israel will not allow Iran to get nuclear weapons. If Israel is forced to stand alone, Israel will stand alone," he said after days of overtures by Iranian President Hassan Rouhani, which included a number of US television interviews.
Western negotiators are to hold new talks with Iranian representatives in Geneva this month in a first test of the overtures.
International sanctions over what the West says is a nuclear weapons programme have badly hit Iran's economy and its leaders have made it clear they are looking for relief.
Kerry on Thursday moved to reassure Israel, saying no-one in the US administration would be won over by the change in tone since Iran's new leader came to power, a period that has been marked by a huge upswing in diplomacy from the pariah state.
"We're going to look very, very carefully at this. We hope it could work because we think the world will be better off, the Middle East will be better off, Iran will be better off, Israel will be better off, if there is a way to achieve a verified, certainty to the elimination of a nuclear programme for weapons purposes in Iran," Kerry said.
"The test we face now over these next weeks and months, not a long period of time, over a short period of time, is to determine whether or not that is in fact what Iran intends."