MOSCOW — The brother of an American man being held in Moscow on suspicion of spying is raising the possibility that his sibling is being used as a pawn in a potential exchange for a Russian woman behind bars in the U.S.

Paul Whelan's brother told The Associated Press that he can't help but question if the events are connected.

"You look at what's going on and you wonder if this is just a large game of pieces being moved around," David Whelan told the AP via Skype from Newmarket, Ontario. "You start to wonder if all of these things are connected. But at the same time, they could just be arbitrary events."

Asked about the matter by reporters at the White House on Sunday, President Donald Trump said: "We're looking into that."

Paul Whelan, a former U.S. Marine who also holds Canadian, British and Irish citizenship, was detained in Moscow in late December. His arrest has led to speculation that Russia could be using him to bargain for a Russian woman who has pleaded guilty to acting as a foreign agent in the U.S.

But Russian Deputy Foreign Minister Sergei Ryabkov said Saturday that discussing a possible swap involving Whelan and Maria Butina would be premature because Whelan hasn't been formally charged, according to Russian news agencies.

"As to the possibility of exchanges of one sort of another, it's impossible and incorrect to consider the question now when an official charge hasn't even been presented," Ryabkov was quoted as saying by state news agency RIA-Novosti.

"Charges will be presented in the near future," he said, according to the Interfax agency.

Some Russian news reports earlier cited unnamed sources as saying Whelan had been indicted on espionage charges that carry a possible prison sentence of 20 years.

Russian officials haven't given details of Whelan's suspected activities and he was initially identified only as an American. His concurrent Canadian, British and Irish citizenships became known on Friday.

U.S. Ambassador Jon Huntsman Jr. visited Whelan on Wednesday in Moscow's Lefortovo Prison, a 130-year-old facility noted for strict conditions. Britain, Canada and Ireland have applied for consular access to him.

Whelan, 48, was discharged from the Marines for bad conduct. He works as the global security director for a U.S. automobile parts manufacturer and lives in Michigan. His family has said he was in Moscow to attend a wedding.

His brother, David, told the AP that Whelan loves to travel and likes to "interact with the people in the places that he goes," but that Whelan would be too "conspicuous" to be selected as a spy.

David Whelan said his family had had no direct contact with Paul and had received no details about the alleged espionage charges from either the Russian or U.S. governments.

"He likes to go places and Russia happens to be a place where he knows people and when he's there, he does go and visit," David Whelan said.

Paul Whelan established an account on VKontakte, a social media service similar to Facebook that is popular among Russians, which showed he had scores of contacts in Russia. Many attended universities affiliated with the military, civil aviation or technical studies. Many share his interest in sports and firearms.

Also Saturday, the Foreign Ministry said it was seeking information about a Russian who was arrested Dec. 29 in Saipan in the Northern Mariana Islands, a U.S. commonwealth in the Pacific. The ministry said Sergei Makarenko was sent to Florida after his arrest and it wants consular access to him.

The Saipan Tribune reported that Makarenko was indicted in 2017 in Florida for the alleged illegal shipment of military goods to Russia.

Konstantin Kosachev, head of the international affairs committee of the upper house of the Russian parliament, said Makarenko's arrest was "the latest attack on a citizen of Russia outside the framework of international law," Interfax reported.

Bridget Virgo reported from London.