US Treasury Secretary Jacob Lew defended negotiations for a nuclear deal with Iran in a speech to a pro-Israel audience on Sunday.
Lew was interrupted several times by heckling from the audience at an annual New York conference sponsored by The Jerusalem Post as he laid out the US administration's position on the nuclear negotiations, AFP reported.
"A diplomatic solution is the best, most enduring path to achieve our goal of keeping Iran from obtaining a nuclear weapon," he said.
"But we have also been clear that we remain steadfast in our determination to take any steps necessary to prevent Iran from obtaining nuclear weapons. That is not just important to Israel's security but America's security."
Iran denies its nuclear activities may have any military objectives, saying the program is solely for peaceful purposes such as generating electricity and medical research.
Lew rejected reports that Iran's uranium stockpile has grown over the 18 months of the negotiations, and insisted that an interim agreement has succeeded in containing its nuclear program.
Iran "has halted and scaled back key elements of its nuclear program. And we have gained unprecedented insight into Iran's nuclear activities," he said.
"Even though Iran's stockpile of uranium has gone up and down at various times over the past 18 months, this was something we anticipated and at each of the deadlines that have been set, Iran's uranium stockpile levels have been within the levels that were agreed to."
The New York Times reported on June 1 that international inspectors found that Iran's stockpile of nuclear fuel increased about 20 percent over the past 18 months. Lew, who is an orthodox Jew, insisted that the United States was "not operating on an assumption that Iran will act in good faith."
"This deal will only be finalized if the connective tissue of the agreement meets a tough standard of intense verification and scrutiny," he said.
"If we reach an agreement and Iran ends up flouting its obligations, we will know, and we will have preserved all our options -- including economic and military measures -- to make sure that Iran can never acquire a nuclear weapon."
The UN nuclear agency's reports issued after Iran and the major powers reached the interim deal in Geneva in late 2013 have confirmed that Tehran has met all its commitments under the accord.
