WASHINGTON, April 11 (UPI) -- Two of Republican presidential contender John McCain's top advisers and fundraisers acknowledge they have had lucrative foreign lobbying contracts.

While legal, some experts say such cross-representation situations pose potential ethical problems, The Washington Times reported Friday.

"I'm not sure it's a good idea that one person plays all these roles," said Toni-Michelle C. Travis, a political analyst and professor of government at George Mason University told the Times. "The entanglements become greater and greater, and that can lead to conflict-of-interest questions at some point.

"People are slipping across the lines to play multiple roles."

The firms of McCain senior adviser Charlie Black and campaign co-chairman Thomas Loeffler have earned millions from foreign governments, lobbying the White House, Congress and others, the Times said.

Loeffler, a former Texas congressman whose firm has received millions of dollars from Saudi Arabia, said he had never spoken about his clients with McCain, the senator from Arizona, who he said often voted against his clients' interests.

Black expressed that he possesses a similar ability to keep his interests separated.

"If an issue comes up, I don't participate in the discussion," he said.

Hundreds of lobbyists are registered to work for foreign clients.