Kapolei, Hawaii (AP) – Defending his efforts to halt the Iranian nuclear threat, President Barack Obama said Sunday that the economic sanctions against the country have had "enormous bite," and that he is united with Russian and Chinese leaders in ensuring Iran does not develop an atomic weapon and unleash an arms race across the Middle East.

The president, at a news conference that closed an Asia-Pacific economic summit, did not specifically say he would consider military action if Tehran were to persist in arming itself with a nuclear weapon. But he added: "We are not taking any options off the table. Iran with nuclear weapons would pose a threat not only to the region but also to the United States."

Obama's stand came laced with presidential politics. Republican presidential contenders, including former Massachusetts governor Mitt Romney, have assailed Obama for not doing more to keep Iran from getting nuclear weaponry. Said Obama: "Is this an easy issue? No. Anyone who claims it is is either politicking or doesn't know what they're talking about."

The sun setting over the ocean behind him in Hawaii, Obama fielded questions across domestic and foreign fronts. He prodded China on its economic policy, pledged to keep fighting Republicans over his largely stalled jobs bill, reflected on the hurt of the Penn State sex abuse scandal and challenged a key congressional debt panel without dropping any veto threats.

Obama is in the midst of a nine-day trip far from Washington, first to host the yearly Asia-Pacific Economic Cooperation summit, then on to Australia and Indonesia. Surrounded by tropical paradise, he said he and the leaders of 20 others nations spanning the Pacific Rim were "here for business. We're here to create jobs."

For the president, the news conference was his first opportunity to address a report Friday from the International Atomic Energy Agency that provided new evidence that Iran's nuclear program includes clandestine efforts to build a bomb.

The report alleges Iran has been working to acquire equipment and weapons design information, testing high explosives and detonators and developing compute models of a warhead's core. It is the most unequivocal evidence yet that the Iranian program ranges far beyond enriching uranium for use in energy and medical research, as Iran insists.

In meetings Saturday with Russian President Dmitry Medvedev and Chinese President Hu Jintao, Obama sought to rally support for putting new pressure on Iran's regime. But there was little public sign either country was ready to drop its opposition to additional sanctions through the United Nations.

Obama insisted the countries are working on the next steps.

"All three of us entirely agree on the objective which is making sure that Iran does not weaponize nuclear power and we do not trigger a nuclear arms race in the region," Obama said. "That's in the interest of all of us. We will be consulting with them carefully over the next several weeks to look at what other options we have available to us."

The U.S. has already slapped sanctions on dozens of Iranian government agencies, financial and shipping companies as well as officials over the nuclear program and could target additional institutions like Iran's Central Bank. And the U.N. has imposed four rounds of sanctions that have caused economic hardship in Iran.

"The sanctions have enormous bite and enormous scope," Obama said.

Pressed on criticisms from the Republican presidential candidates, Obama said he would hold his own fire until the opposition party settles on a person to challenge him.