BANGKOK, Thailand — Thai prosecutors announced Thursday that they plan to challenge a lower court ruling that rejected a U.S. request to extradite suspected Russian arms dealer Viktor Bout.

That means Bout, 42, dubbed the “Merchant of Death” for allegedly shipping arms that have fueled conflicts in Africa, the Middle East and Latin America, will spend several more months in a Thai jail pending the appeal. He had hoped for release as early as Friday.

Bout was arrested in March 2008 at a luxury hotel in Bangkok as part of an elaborate sting in which U.S. agents posed as arms buyers for the Revolutionary Armed Forces of Colombia, or FARC, which Washington classifies as a terrorist organization.

The Bangkok Criminal Court rejected the extradition request Tuesday because it deemed FARC a political movement, rather than a terrorist group, which meant that Bout’s alleged crimes were political offenses, ruling out extradition under a U.S.-Thai treaty.

“The prosecutor has filed its intention to appeal the case as requested by the U.S. officials,” said Sirisak Tiyatan, the director general of the attorney general’s foreign division. The appeal must be filed within 30 days.

The United States, which had expressed support for the appeal, had no immediate comment.

Bout’s lawyer Lak Nitiwatanavichan said he was confident the rejection would be upheld on appeal and his client eventually freed.

“Let them appeal. We will fight with the same defense,” Lak said. “They have no case. I don’t see why the court would rule differently.”

Bout, a former Soviet Air Force officer, has been linked to some of the world’s most notorious conflicts, allegedly supplying arms to former Liberian dictator Charles Taylor and Libyan leader Moammar Gadhafi. He has repeatedly denied the accusations.

The United States is seeking Bout’s extradition on charges he conspired to sell millions of dollars worth of weapons to FARC, including more than 700 surface-to-air missiles, thousands of guns, high-tech helicopters and airplanes outfitted with grenade launchers and missiles. He has been indicted on four terrorism-related charges in New York and could face up to life in jail.

Bout’s nickname, the “Merchant of Death,” came in 2000 from a minister at Britain’s Foreign Office who was concerned that Bout was ferrying weapons around Africa. He has been the subject of UN sanctions, a Belgian money-laundering indictment and an assets freeze by the United States.