UNITED NATIONS, (Reuters) – The U.N. Security  Council imposed a fourth round of sanctions in as many years on  a defiant Iran yesterday over a nuclear programme the West  suspects is aimed at developing atomic weapons.

Iran insisted it would go ahead with the uranium enrichment  at the center of the dispute. President Mahmoud Ahmadinejad  said the U.N. resolution was “valueless” and should be thrown  “in the waste bin like a used handkerchief.”

But Russia and China, which have strong economic ties with  Tehran and have at times resisted sanctions, fully backed the  new U.N. move to blacklist dozens of Iranian military,  industrial and shipping firms.

U.S. President Barack Obama said the sanctions, which also  provide for inspections of suspect cargoes to and from Iran and  tighten an arms embargo, would be vigorously enforced.

The resolution followed five months of arduous negotiations  between the United States, Britain, France, Germany, China and  Russia. With 12 votes in favor, it received the least support  in the 15-nation council of the four Iran sanctions resolutions  adopted since 2006.

Brazil and Turkey, angry at the West’s dismissal of an  atomic fuel deal with Iran that they said made new sanctions  unnecessary, voted against. Lebanon, where the Iranian-backed  militant group Hezbollah is in the government, abstained.

Brazilian President Luiz Inacio Lula da Silva called the  resolution a mistake and his foreign minister said he doubted  the sanctions would have any impact. But U.S. Secretary of  State Hillary Clinton said in Colombia they would “slow down  and certainly interfere with” Iran’s nuclear ambitions.

The sanctions vote was delayed for more than an hour as the  Brazilian, Turkish and Lebanese delegations awaited  instructions from their capitals. Western diplomats said that  Lebanon’s abstention came after the Lebanese cabinet split  14-14 over whether to oppose the resolution or abstain.

The four Western powers had wanted tougher measures — some  targeting Iran’s energy sector — but Beijing and Moscow  succeeded in diluting the steps outlined in the resolution. “This council has risen to its responsibilities. Now  Iran should choose a wiser course,” U.S. Ambassador Susan Rice  told the council after the vote.

Iran denies Western allegations that it is seeking atomic  weapons, insisting that it only wants peaceful nuclear energy.

Tehran’s envoy to the U.N. nuclear watchdog in Vienna said  the sanctions would not alter Iran’s nuclear program. “Nothing  will change. The Islamic Republic of Iran will continue uranium  enrichment activities,” Ambassador Ali Asghar Soltanieh said.

China, which had hesitated for months before joining talks  on new sanctions in January, called for full implementation of  the new measures and urged Tehran to comply with international  demands about its enrichment program.

In Washington, Obama said the new sanctions were the most  comprehensive that Iran had faced and sent an unmistakable  message. “We will ensure that these sanctions are vigorously  enforced, just as we continue to refine and enforce our own  sanctions on Iran,” he said. Israel, which has hinted it could bomb Iran’s nuclear  facilities the way it did Iraq’s in 1981, said the new  sanctions were an important step, but called for even broader  economic and diplomatic measures.

Russia’s Foreign Ministry may have had Israel in mind when  it announced that the measures in the resolution “exclude the  possibility of employing force.”

The resolution calls for measures against new Iranian banks  abroad if a connection to the nuclear or missile programs is  suspected, as well as vigilance over transactions with any  Iranian bank, including the central bank.

It also blacklists three firms controlled by Islamic  Republic of Iran Shipping Lines and 15 belonging to the Islamic  Revolutionary Guard Corps, as well as calling for setting up a  cargo inspection regime like one in place for North Korea.