The United States is committed to reaching a final deal with Iran by July which would ensure Tehran will never be able to produce nuclear weapons, Undersecretary of State Wendy Sherman said Saturday.

Speaking in Jerusalem, the top US negotiator in the ongoing negotiations between Iran and the P5+1 world powers said there was only one measure of success, “and that is if an agreement means that Iran will never obtain a nuclear weapon and that the international community will have assurance in the exclusively peaceful nature of a nuclear program in Iran.”

The US, she said, was looking for “concrete actions” by Iran, and she intended to tell Israeli leaders that a comprehensive agreement would not be “about what we believe, it is about what we see, what can be verified, what can be monitored.”

Sherman arrived in Israel from the latest round of talks between world powers and Iran in Vienna and spoke to reporters in Jerusalem.

The undersecretary said the US had begun “tough negotiations” that will continue through July, by which time she hopes the sides will reach a comprehensive agreement.

“We have set a framework and a timetable for the negotiations, but this is a very complex negotiation and I very much look forward to the talks I will have here in Israel,” she said.

Sherman expressed appreciation for the “input, ideas, points of view” she has received from Israeli leaders during her visits between summits.

“Sometimes we agree, sometimes we don’t agree, but what is critical is to have that input as we move forward to ensure the security of Israel and the security of the United States and the security of the world,” Sherman said.

The sides are set to reconvene in Vienna on March 17, after having met in the Austrian capital earlier this week.

The talks are designed to build on a first-step deal reached in November that commits Iran to initial nuclear curbs in return for some easing of sanctions. The deal can be extended by mutual consent after six months.

Under terms of that accord, Iran has already begun to carry out a series of steps. These include diluting or converting its stockpile of higher enriched uranium and not to make any more for the next six months.

Iran also agreed not to increase its stockpile of lower-enriched uranium and not to set up new centrifuges at its enrichment plants, as well as to allow rigorous oversight by the UN nuclear agency.

Sanctions being suspended during this interim agreement include those on Iran’s petrochemical exports, its trade in gold and precious metals, its car industry and the supply of parts for Iran’s civil aviation industry. No new sanctions will be imposed while the first-step deal remains in effect.