Iran's Foreign Ministry says tougher U.S. sanctions are "doomed to fail"
Head of Revolutionary Guard vows military force will defend Iranian revolution
U.S. puts sanctions on Iran's Revolutionary Guard, banks, individuals
Sanctions mean financial assets of Revolutionary Guard, others, are frozen
(CNN) -- The leader of Iran's Revolutionary Guard vowed Friday that the military group was ready to defend the Iranian revolution after the U.S. imposed sanctions against it amid simmering tensions over Tehran's refusal to halt its nuclear program.
Washington accuses the Revolutionary Guard, its elite Quds Force and a number of Iranian banks and companies of supporting nuclear proliferation and terror-related activities.
But General Mohammad Ali Jafari told Iranian state news agency IRNA: "They have applied all their efforts to reduce the efficiency of this revolutionary body. Now as always, the corps is ready to defend the ideals of the revolution more than ever before."
An Iranian Foreign Ministry spokesman also said sanctions were "doomed to fail," calling them "worthless and ineffective" and criticizing the U.S. for pursuing confrontational policies.
Meanwhile, speaking Thursday in Kuwait, Iranian Interior Minister Mostafa Pour-Mohammadi warned that any military attack on Iran would be met with a "crushing response."
"We will defend our security and our country in the strongest way," said Pour-Mohammadi, quoted by the IRNA Web site.
"The U.S. is well aware that it might be easy to start such an action against Iran but ending that would not be then in the hands of U.S. officials. Such action will definitely end up in U.S. collapse."
The measures, announced Thursday by U.S. Treasury Secretary Henry Paulson and U.S. Secretary of State Condoleezza Rice, are the first time the U.S. has attempted to punish another country's military through sanctions.
"The Iranian regime's abilities to pursue nuclear and ballistic missile programs in defiance of U.N. Security Council resolutions depends on its access to international, commercial, and financial systems," said Paulson.
The Quds Force had provided "lethal support" to the Sunni-dominated Taliban for use against U.S. and NATO forces, while the Iranian Revolutionary Guard had "been outspoken about its willingness to proliferate ballistic missiles capable of carrying weapons of mass destruction," according to a U.S. Treasury Department statement.
The U.S. also clamped down on the activities of three top Iranian financial institutions -- Bank Melli, Bank Mellat, and Bank Saderat -- all of which had "facilitated Iran's proliferation activities or its support for terrorism."
"Iran also funnels hundreds of millions of dollars each year through the international financial system to terrorists," said Paulson.
"We call on responsible banks and companies around the world to terminate any business with Bank Melli, Bank Mellat, Bank Saderat, and all companies and entities (of the corps)."
The U.S. has been working with other world powers to halt what they believe is Iran's intent to develop a nuclear arsenal. Iran says it is pursuing nuclear energy for a civilian power program, and it has refused to comply with a U.N. Security Council call to halt its production of enriched uranium.
China, which has resisted U.S. efforts to impose further measures against Tehran, said on Friday that new sanctions could increase tensions.
"Dialogue and negotiations are the best approach to resolving the Iranian nuclear issue," China's foreign ministry said in a brief statement to The Associated Press.
"To impose new sanctions on Iran at a time when international society and the Iranian authorities are working hard to find a solution to the Iranian nuclear issue can only complicate the issue."
Russian President Vladimir Putin said Thursday that the Kremlin would not back new international sanctions, AP reported.
"Why worsen the situation and bring it to a dead end by threatening sanctions or military action?" Putin said in comments apparently directed at the U.S. "Running around like a madman with a razor blade, waving it around, is not the best way to resolve the situation."
Rice said she was willing to meet with her Iranian counterpart and other Security Council members "any time, anywhere" to discuss the country's nuclear plans.
"We will be open to the discussion of any issue," said Rice. "But if Iran's rulers choose to continue down a path of confrontation, the United States will act with the international community to resist these threats of the Iranian regime."
Mohamed ElBaradei, director-general of the United Nations' International Atomic Energy Agency, has criticized U.S. rhetoric on Iran and said last month that Iran's declared nuclear material has not been diverted from peaceful use.
CNN's Elise Labott and Shirzad Bozorgmehr contributed to this report.