U.S. President Barack Obama said Tuesday his administration will develop "a significant regime of sanctions," over the next several weeks targeting Iran.

Obama said Iran has refused to accept a UN-backed uranium swap deal, which he claimed was "the most obvious attempt" of the international community to engage with Tehran, accusing Iran of pursuing "a course that would lead to weaponization."

He said since Iran refused to engage, "then the next step is sanctions."

"What we are going to be working on over the next several weeks is developing a significant regime of sanctions," he announced.

As to how the sanctions tactic will be played out, Obama said the administration is "going to be looking at a variety of ways in which countries indicate to Iran that their approach is unacceptable," and the United Nations "will be one aspect of that broader effort."

Obama said he is confident that "the international community is unified around Iran's misbehavior" in the area of applying more pressure to Tehran. He said he is pleased ...to see how forward- leaning the Russians have been on this issue."

Iran declared on Tuesday it had started the process of producing 20-percent enriched uranium inside the country. Obama said Iran "hasn't been serious about solving what is a solvable dispute."

He made the remarks during an unannounced visit to the White House briefing room, where Press Secretary Robert Gibbs was supposed to be holding a regular briefing.

Under a draft deal brokered by the International Atomic Energy Agency, the UN nuclear watchdog, most of Iran's existing low-grade enriched uranium should be shipped to Russia and France, where it would be processed into fuel rods with the purity of 20 percent.

Iran has been at the center of an international dispute over its nuclear plan. The United States and its Western allies have been accusing Iran of secretly developing nuclear weapons under the disguise of a civilian program. Iran has denied the accusation and stressed its nuclear program is only for peaceful purposes.