Israel was left fuming on Monday after U.S. Secretary of State Hillary Clinton announced that the U.S. was "not setting deadlines" for Iran and still considered negotiations to be "by far the best approach" to prevent Iran from developing nuclear weapons.

"Hillary Clinton is speeding up the Iranian centrifuges with her erroneous public comments,” senior diplomatic sources in Jerusalem said. “Without a clear red line, Iran will not halt its race for nuclear weapons." The source added that "not only do Clinton's comments not deter Iran, they actually appease it."

In an interview with Canadian television on Sunday night, Prime Minister Benjamin Netanyahu said that the U.S. and Israel were discussing the need for red lines to halt Iran's nuclear program. He also said, "I don't think that they [the Iranians] see a clear red line, and I think the sooner we establish one, the greater the chances that we won't need other types of action."

But in Washington on Monday, State Department spokeswoman Victoria Nuland echoed Clinton's comments, telling reporters, "It is not useful to be ... setting deadlines one way or another," or to outline "red lines" for how far the U.S. could allow Iran's nuclear program to advance.

She repeated that U.S. President Barack Obama had stated unequivocally that the U.S. will not allow Iran to obtain a nuclear weapon, and that U.S. support for Israel's security was unwavering. But she said she would not speak about ongoing discussions between the U.S. and Israel, calling such talk "not helpful for the diplomacy."