Washington's UN ambassador Samantha Power said Monday that compliance with the Iran nuclear deal was so far "strong", but warned Tehran was still helping fuel conflict and remained a threat.

"What this deal does if implemented -- and so far the implementation has been strong but it's very early days -- is it cuts off the pathways to a nuclear weapon and it gives us much more visibility into Iran's programme than we had before," Power told students during a visit to Israel and the Palestinian territories.

She added later that "Iran of course is still a threat. Iran is supporting terrorism. Iran is supporting parties to conflict like the Assad regime (in Syria)".

Last July's Vienna agreement between Iran and the permanent five members of the UN Security Council plus Germany (P5 plus one) sees sanctions lifted in return for Tehran ensuring its nuclear programme remains for civilian use.

Israel strongly opposed the deal with its arch-foe, with Prime Minister Benjamin Netanyahu warning it would not block Iran's path to nuclear weapons.

He also said lifting sanctions would allow Iran to further back proxy militants in the region, including Israeli enemies such as Hezbollah.

Netanyahu's outspoken criticism of the accord, particularly in a speech to the US Congress, led to a rift with US President Barack Obama's administration.

He has since scaled back his rhetoric, and the United States and Netanyahu's government are currently negotiating a new 10-year defence aid package expected to be an increase over the current $3.1 billion Israel receives annually.

Power has met Israeli and Palestinian leaders during her visit, expected to end Tuesday.

She said Washington's aim was to move the two sides towards "being in a position to restart the negotiations, which is not a position they are in right now".

Power met Netanyahu earlier Monday and said they discussed "steps that could be taken to preserve prospects" for a two-state solution.

They also discussed the conflict in Syria and the threat from the Islamic State group, she said.

Power's visit comes amid a wave of Palestinian knife, gun and car-ramming attacks that erupted in October.

Since then, 172 Palestinians and 26 Israelis, as well as an American, a Sudanese and an Eritrean have been killed, according to an AFP count.

Most of the Palestinians were killed while carrying out attacks, but others died during clashes and demonstrations.