* FSB says American worked under cover at embassy
* Man with disguises and cash detained overnight, FSB says
* Awkward timing as U.S. and Russia seek joint Syria approach (Adds U.S. comments, material from video about alleged target)
Russia expelled a U.S. diplomat on Tuesday after saying he had been caught red-handed with disguises, special equipment and wads of cash as he tried to recruit a Russian intelligence agent to work for the CIA.
Apparently detained in an incongruous-looking blond wig, with props reminiscent of a schoolboy's spy kit, U.S. Embassy Third Secretary Ryan Fogle hardly looked like a Cold War secret agent.
But the announcement still came at an awkward time for Washington and Moscow as they try to improve relations and bring the warring sides in Syria together for an international peace conference. Nevertheless, there was little sign that either country wanted to escalate the affair beyond a minimum response.
The Russian Foreign Ministry summoned U.S. Ambassador Michael McFaul to discuss the case on Wednesday and released a statement ordering Fogle to leave Russia.
"Such provocative actions in the spirit of the Cold War will by no means promote the strengthening of mutual trust," it said.
In Washington, U.S. State Department spokesman Patrick Ventrell suggested the episode was unlikely to affect broader U.S.-Russian relations or plans for the Syria conference.
"I'm not sure I would read too much into one incident one way or another," Ventrell said. He confirmed that an embassy officer had been briefly detained, but declined further comment.
Russia's Federal Security Service (FSB) said Fogle had been detained overnight carrying "special technical equipment", a disguise, a large sum of money and instructions for recruiting his target.
Russian television showed grainy footage of a man identified as Fogle, in a blond wig, being arrested and pinned to the ground.
WIGS, GLASSES AND COMPASS
A photo published by the state-run Russia Today channel on its website showed two wigs, apparently found on him, as well as three pairs of glasses, a torch, a mobile phone and a compass.
Also displayed was a wad of 500-euro ($650) notes and a letter printed in Russian and addressed to a "Dear friend".
"This is an advance from someone who has been highly impressed by your professionalism, and who would highly value your cooperation in the future," the letter said. It offered an intial payment of $100,000, and $1 million a year for long-term cooperation, plus possible bonuses for useful information.
The FSB, a successor to the Soviet KGB, said Fogle worked for the Central Intelligence Agency and that he had been handed over to embassy officials at some point after his detention.
RT footage showed a Russian official haranguing Fogle, a senior U.S. embassy official and two others in an FSB office. The speaker says Fogle twice called his target - an officer involved in counterterrorism in the restive North Caucasus - and proposed that he spy for the United States.
McFaul, frequently been criticised by Russian media for his critical views on Russia, was holding a question-and-answer session on Twitter as the detention was announced, but refused to take questions on the matter.
More than two decades after the end of the Cold War, spying - and spy scandals - are still far from unusual.
The last significant one was in 2010, when 10 Russian agents including Anna Chapman were arrested in the United States and later deported in exchange for four Russians imprisoned on charges of spying for the West.
THAW TO GO ON?
U.S.-Russian relations had thawed markedly under Obama's first-term "reset" of ties, but have chilled again since Putin, himself a former KGB spy, returned to the presidency a year ago.
Putin has accused the United States of encouraging protests against him, and Russia has ejected the U.S. Agency for International Development and curbed U.S.-supported NGOs in moves it says are aimed at preventing foreign meddling.
But both Obama and Putin have signalled they want to patch things up again, and the countries are trying to improve counterterrorism cooperation after the Boston Marathon bombings.
FBI chief Robert Mueller visited Moscow for talks last week.
Detained Boston bombing suspect Dzkhokhar Tsarnaev and his brother Tamerlan, who was shot dead by police, are ethnic Chechen brothers who lived briefly in the Russian Caucasus.
Samuel Charap, senior fellow at the International Institute for Strategic Studies, said Moscow's handling of the incident would show whether it wanted to continue the recent thaw.
"Does the Russian government do what the U.S. did in 2010, and act quickly to defuse the issue, or does it use the incident to escalate tensions? That is the key question now."
Most analysts said the row would blow over.
"On the higher level ... both countries have always been adept at isolating these incidents from wider relations," said Matthew Clements, Eurasia analyst at IHS Janes.
Alexei Pushkov, a Kremlin ally who chairs the international affairs committee in Russia's lower parliament house, said the scandal would not get in the way of talks between Russian Foreign Minister Sergei Lavrov and U.S. Secretary of State John Kerry on how to tackle Syria's civil war.