The White House said Monday that the door of negotiation over Iran's nuclear program "is of course still open" before the international community decides on the "next steps."

"The door is of course still open for Iran to do the right thing and live up to its international obligations," White House spokesman Bill Burton told reporters, adding that the United States will be "going through the appropriate process to try to get them to the table and do exactly what they're supposed to do."

According to the spokesman, U.S. President Barack Obama would convene his national security team this week to determine "what the next steps are."

Earlier on Monday, Secretary of State Hillary Clinton said the United States has been discussing with other major powers on sanctions against Iran, and that the aim of the sanctions is to pressure the Iranian government and the Islamic Revolutionary Guard Corps.

Clinton's remark came after Tehran rejected a Dec. 31 deadline set by the United States for Iran to accept a deal for swapping its low-enriched uranium for nuclear fuel outside Iran and demanded a simultaneous exchange inside the country.

Iran's Foreign Minister Manouchehr Mottaki has said that the international community has "only one more month" to decide whether it wants to sell nuclear fuel to Iran or swap nuclear fuel for Iran's low-enriched uranium.

"Otherwise, Tehran will enrich uranium to a higher purity needed for the fuel," said Mottaki, adding that "This is an ultimatum."

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

The higher-level enriched uranium would be transported back to Iran to be used in a research reactor in Tehran for the manufacture of medical radioisotopes.

The United States and its Western allies have been accusing Iran of secretly developing nuclear weapons under the disguise of civilian nuclear power. Iran has denied the accusation and stressed its nuclear program is only for peaceful purposes.

The United States has threatened another round of UN sanctions against Iran if it does not abide by the year-end deadline.