WASHINGTON  A Russian businessman regarded by the United States as one of the world’s most notorious arms dealers was arrested in Thailand on Thursday as part of an American-led sting operation. He was promptly charged in the United States with conspiracy for trying to smuggle missiles and rocket launchers to rebels in Colombia.

The businessman, Viktor Bout, 41, is suspected of supplying weapons to the Taliban and Al Qaeda and of pouring huge arms shipments into Africa’s civil wars with his own private air fleet. He was arrested by the Thai authorities at a hotel in Bangkok in an operation in which undercover investigators posing as rebels from the Revolutionary Armed Forces of Colombia, or FARC, sought to purchase millions of dollars in arms.

Federal prosecutors in New York said they would seek the extradition of Mr. Bout (pronounced boot) and an associate, Andrew Smulian, who was also detained in Bangkok on Thursday, to stand trial in the United States on a charge of conspiracy to provide material support to a foreign terrorist organization. Although American officials said Thailand appeared to be eager to be rid of Mr. Bout, it was not known when he would be brought to the United States.

Michael J. Garcia, the United States attorney for the Southern District of New York, said that Mr. Bout “was apprehended in the final stages of arranging the sale of millions of dollars of high-powered weapons to people he believed to represent a known terrorist organization, the FARC.”