Secretary of State Condoleezza Rice said Wednesday that Iran has given a "disappointing and incomplete" response to an international deal to end suspicious nuclear activities and that world powers may have no choice but to haul Iran before the U.N. Security Council.

Iran ruled out responding this week to international incentives to suspend disputed portions of its nuclear program. The United States and other nations wanted an answer by Wednesday on whether Iran would meet terms to begin negotiations on a package of economic and energy incentives for Iran in exchange for at least the short-term end to Tehran's rapidly advancing program to enrich uranium.

"The indications are that Iran's response has been disappointing and incomplete," Rice told reporters aboard her flight from Washington to Paris early Wednesday. "If that is indeed the case, we've always said we were either on the path to negotiations or we're on the path to the Security Council."

Foreign ministers from the six countries that made the proposal — the five permanent members of the Security Council plus Germany — were meeting Wednesday in Paris.

The six are pushing for an agreement before world leaders meet this weekend in Russia for the Group of Eight summit of leading industrial democracies.

If Iran agrees to the group's terms for negotiations, it would mean the first high-level face-to-face talks between the United States and Iran after more than a quarter century of estrangement.

The group's meeting is likely to produce a strongly worded statement that restarts efforts for possible Security Council punishment for Iran if it does not suspend uranium enrichment and agree to talks.

Enrichment can produce fuel for a civilian reactor or fissile material for a bomb. The U.S. and its allies suspect Iran's nuclear program is cover for a weapons program, despite Tehran's repeated denials.

Any real punishment or coercion at the Security Council is a long way off, but Western diplomats said they may begin writing a resolution within days if there is no movement toward talks this week.

"If we go to the Security Council we'll take our time in terms of putting together the best response," to make sure Iran understands that it cannot continue to pursue enrichment while talks are ongoing, and that it also understands it can still choose to bargain, Rice said.

The Security Council would also make clear the consequences of rejecting the deal, Rice said.

That would put the United States, European allies and others back where they started last year, when Iran rejected a previous European offer and later resumed a broad program of nuclear research and development it had shuttered during earlier talks.

Rice offered to join those talks in May on condition that Iran reimpose a moratorium on uranium enrichment. The U.S. offer was a gambit that the prospect of talks with the largest world power and Iran's principal adversary would persuade Iran that the offer was serious, and a show of faith to European partners who were growing restless with the incremental and inconclusive Iran diplomacy.

"What we have been able to do test whether the Iranians simply wanted a good path of negotiations or whether they are determined to defy the international community," Rice said.

"Apparently, and I just want to say apparently, they have decided that they want to move ahead with a program that is unacceptable to the international community. That then means we would be on the path of the Security Council."

The Security Council has already delivered a mild rebuke to Iran. If its permanent, veto-holding members agreed, the council could move on to impose coercive or punitive measures. Those could include economic or political sanctions, financial or travel restrictions, or even an oil embargo. The toughest measures are unlikely to win approval from Russia and China, traditional commercial partners of Iran that hold vetoes.

Iran repeatedly has said it will not respond to the offer before August.

On Tuesday, Iranian nuclear negotiator Ali Larijani warned that talks on his country's atomic program will be a "long process," and said "ambiguities must be removed first in order to have serious talks."

Larijani spoke after meeting with European Union foreign policy chief Javier Solana.

The Iranian negotiator refused to elaborate on the nature of the perceived ambiguities, but he asked for patience.

Larijani warned against sending the matter to the Security Council for possible sanctions, calling it "the wrong way" to solve the impasse.

"It is not difficult to disrupt negotiations by making harsh comments," Larijani said.