President Barack Obama vowed Sunday to "keep up pressure" on Tehran to prevent the Islamic republic from obtaining nuclear weapons, as he condemned its support for extremists in the region.

Outlining US and UN sanctions imposed on Iranian President Mahmoud Ahmadinejad's regime, Obama said Iran is now "virtually cut off from large parts of the international financial system."

"We're going to keep up the pressure... So let me be absolutely clear -- we remain committed to preventing Iran from acquiring nuclear weapons," he added to roaring applause from the audience at the pro-Israel lobby AIPAC Policy Conference.

The United States, Russia, China, France, Britain and Germany have engaged in on-again, off-again talks with Iran aimed at halting its uranium enrichment program, which Washington fears masks a drive to produce a nuclear weapon. Iran denies the charges and claims its program is peaceful.

Obama also pointed to Iranian "hypocrisy" in "claiming to support the rights of protesters while treating its own people with brutality."

He said Iran was funding, arming and otherwise supporting violent extremists.

"So we will continue to work to prevent these actions, and we will stand up to groups like Hezbollah, who exercise political assassination and seek to impose their will through rockets and car bombs," said Obama.

Hezbollah, an Iranian-backed Shiite militant group in Lebanon, is blacklisted as a terrorist group by the United States.

The UN Security Council has adopted four sets of sanctions against Iran, the most recent in June last year, over its refusal to suspend uranium enrichment, the sensitive process that lies at the heart of Western concerns.

A panel of experts that monitors the sanctions said Iran was circumventing them but that its nuclear work had been impaired.