Secretary of State Condoleezza Rice and British Foreign Secretary David Miliband on Thursday stepped up warnings to Iran to come clean about its nuclear programs soon or face new sanctions.

Ahead of the release of a new report expected to show that Iran is continuing to deny U.N. experts access to records of its past nuclear activity, the two leading diplomats said Tehran must comply with international demands to halt work that could produce atomic weapons fuel.

They also said Iran, which denies its programs are arms-related, must accept a package of incentives offered by major world powers that it has yet to agree to receive or face consequences at the U.N. Security Council and punitive measures from individual countries.

"There is no doubt that there are further steps that the coalition of states that are working on this could take within the Security Council framework if Iran is not prepared to accept the really quite favorable and quite generous package that has been offered to it," Rice said.

Speaking to reporters accompanying her and Miliband on a visit to California, Rice said the Iranian economy was already suffering because of existing U.S., European and U.N. sanctions and said those would continue to expand without a change in behavior by Iran's leaders.

"They are already paying consequences and, of course, there are other possible courses available to us," she said.

She added that the United States was looking at new steps to cut off more Iranian banks from the international financial system and could do so at any time over the nuclear issue as well as alleged terrorism financing.

"We will continue to designate entities as we find them trying to use the international financial system for ill-gotten gains," Rice said. "We're going to continue to do it and we are going to continue to do it aggressively because Iran should not be in a position of using the banking system to pass profits made from terrorism or proliferation."

The comments came before the release of a new report, expected as early as Friday, from the U.N.'s nuclear watchdog, the International Atomic Energy Agency, that diplomats say will find Iran not cooperating with its experts on accounting for previously undeclared activity.

Miliband said the report would buttress the arguments for those demanding that Tehran come clean.

"What's clear is that the IAEA has reached a really important point with the Iranians where they are not getting answers on the outstanding issues ... that go to the heart of the issue of the confidence that the international community can have with the Iranian regime," he said.

"Iran is not the victim of an international vendetta, it's actually the author of its own misdeeds and they are being exposed by the work that IAEA officials are doing," Miliband added.

Rice said such findings would be devastating for Iran's claim to be fully and transparently cooperating with the IAEA.

"This would be a very serious matter," she said.