WASHINGTON - The U.N. Security Council voted Wednesday to tighten sanctions on Iran over its nuclear program but left in doubt whether the new strictures will slow the regime's expanding nuclear program or force it to the negotiating table.

The 12-2 vote, with one abstention, allowed President Obama to claim a diplomatic win after months of haggling to get two crucial, veto-wielding countries - Russia and China - on his side.

"Actions do have consequences, and today the Iranian government will face some of those consequences," Obama said. He left the door open to diplomacy but said Iran "will find itself more isolated, less prosperous, and less secure" unless it met its obligations under the Nuclear Nonproliferation Treaty.

But the U.N. vote also divided the world powers in a way that make future sanctions seem remote. Analysts said Iran emerged with new diplomatic momentum.

Iranian President Mahmoud Ahmadinejad, on a visit to Tajikistan, dismissed the sanctions as "annoying flies, like a used tissue."

The new sanctions further limit arms sales to Iran, restrict the overseas operations of its banks, add more Iranian companies to a blacklist, and authorize companies to search ships going to or from Iran that might carry prohibited nuclear items.

Despite lobbying from Western powers, Turkey and Brazil voted against the measure. Their recent attempt to broker a deal under which Iran would send some of its uranium abroad to avert sanctions, was rejected by the West and others as inadequate. Lebanon abstained.

The sanctions, the fourth such round since 2006, are aimed at forcing Iran to halt a nuclear program that Western powers believe is aimed at acquiring nuclear-weapons know-how. Iran insists the expanding program is only for peaceful nuclear uses.

While U.S. officials emphasized the importance of Russian and Chinese approval for the sanctions, their support came at the cost of agreements by Western officials to sharply water down the Security Council resolution.

"These are not the crippling sanctions that Secretary of State Hillary Clinton had promised about a year ago," said James Lindsay of the Council on Foreign Relations, who was a National Security Council official in the Clinton administration. "To the contrary."

The United States had hoped to sharply curtail foreign financial services available to Iran and Iranian enterprises. But the sanctions approved Wednesday do not bar many financial services, including insurance or reinsurance, to Iranian individuals or companies.

They also don't limit the Islamic Republic's ability to produce or export oil, its most important export.

Although the sanctions ban the sale of many heavy weapons, countries still will be allowed to sell weapons outside those categories. For instance, Russia still may sell Iran S-300 antiaircraft missiles, which are a deep source of concern to the United States and Israel.

Many provisions of the sanctions resolution are essentially optional.

For instance, the resolution says that governments may inspect ships on the high seas suspected of carrying forbidden items, but only if they have the consent of the country to which a suspicious ship is registered.

The Obama administration hopes to magnify the effect of the U.N. sanctions by spurring other countries to impose tougher layers of sanctions of their own.

European Union officials will meet in a few days to consider sanctions that will expand their list of banned military goods and to tighten enforcement, said George Lopez of the U.S. Institute of Peace.

The Obama administration also is expected to add U.S. sanctions that would give the Treasury Department more authority to crack down on foreign banks and other companies that do business with Iran.

Congress has been pressing for a U.S. ban on petroleum sales to Iran, which produces crude but has limited refining capacity. Under such a ban, the U.S. government would penalize foreign oil companies that sell to Iran. But the White House, fearing such an approach would alienate allies, is expected to resist it.

Unilateral and national sanctions also could hurt international diplomatic efforts. Russia and China have signaled that they oppose the imposition of any further bilateral sanctions affecting Iran's economy or trade.

Israeli officials hailed the Security Council resolution but said it would not by itself change Iran's policies and must be augmented by tough steps by individual nations.

The Iranians have proven adept at working around previous sanctions or finding ways to adjust to them.

Lindsay, of the Council on Foreign Relations, noted, for example, that Iran used to be vulnerable because it received 40 percent of its refined petroleum from abroad. Now, however, it imports less than 25 percent.