Easing pressure on Iran over its nuclear program at this stage would be a "historic mistake," Israeli Prime Minister Benjamin Netanyahu said on Monday.

"It would be a historic mistake to ease the pressure on Iran a moment before the sanctions achieve their objective," he said at the opening of the Israeli parliament's winter session.

In remarks a day before world powers hold a fresh round of talks with Iran over its nuclear program, which Israel and much of the West believes is a front for building a weapons capacity, Netanyahu issued a stark warning over any move to ease sanctions.

"Particularly at this moment we must not give up on them, we must keep up the pressure," he said,.

Any move to let up on Iran would only strengthen its "uncompromising elements" and its supreme leader, Ayatollah Ali Khamenei, "will be perceived as the winner," Netanyahu said.