The United States has decided to designate Iran's Revolutionary Guard Corps, the country's 125,000-strong elite military branch, as a "specially designated global terrorist," according to U.S. officials, a move that allows Washington to target the group's business operations and finances.

The Bush administration has chosen to move against the Revolutionary Guard Corps because of what U.S. officials have described as its growing involvement in Iraq and Afghanistan as well as its support for extremists throughout the Middle East, the sources said. The decision follows congressional pressure on the administration to toughen its stance against Tehran, as well as U.S. frustration with the ineffectiveness of U.N. resolutions against Iran's nuclear program, officials said...

...The order allows the United States to block the assets of terrorists and to disrupt operations by foreign businesses that "provide support, services or assistance to, or otherwise associate with, terrorists."...

..The main goal of the new designation is to clamp down on the Revolutionary Guard's vast business network, as well as on foreign companies conducting business linked to the military unit and its personnel. The administration plans to list many of the Revolutionary Guard's financial operations.

"Anyone doing business with these people will have to reevaluate their actions immediately," said a U.S. official familiar with the plan who spoke on the condition of anonymity because the decision has not been announced. "It increases the risks of people who have until now ignored the growing list of sanctions against the Iranians. It makes clear to everyone who the IRGC and their related businesses really are. It removes the excuses for doing business with these people."...

The key obstacle to stronger international pressure against Tehran has been China, Iran's largest trading partner. After the Iranian government refused to comply with two U.N. Security Council resolutions dealing with its nuclear program, Beijing balked at a U.S. proposal for a resolution that would have sanctioned the Revolutionary Guard, U.S. officials said.

China's actions reverse a cycle during which Russia was the most reluctant among the veto-wielding members of the Security Council. "China used to hide behind Russia, but Russia is now hiding behind China," said a U.S. official familiar with negotiations...