"I think the Federal Reserve has made it clear that they would like to do some increase this year, they didn't say when, but before they make a decision, they want to make sure the unemployment rate in the U.S. isn't likely to rise as a result, but also they have recently said they don't want the currency to strengthen," Rubenstein told CNBC.
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"The Federal Reserve and all central banks want to make sure they have a strong currency, but right now the U.S. is very strong with respect to its dollar and there is some concern that if we increase interest rates even a little bit, it could strengthen the dollar so much so that it would be disequilibrium for the U.S. for Europe and other economies," he said, speaking in Berlin, near the SuperReturn International conference.
"So I think the Federal Reserve is not likely to make a decision until the fall," he added.
Rubenstein's comments came just ahead of Fed Chair Janet Yellen semi-annual testimony in front of the Senate Banking Committee in Washington.
At the address, Yellen described how the central bank's rate-setting policy committee will likely proceed in coming months— an effort to increase the Fed's flexibility and mute any potential market reaction as the central bank approaches its liftoff date for rate increases.
Her remarks struck a decidedly dovish tone in indicating that it would be a while before the central bank's Open Market Committee makes a move on interest rates.
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"The FOMC's assessment that it can be patient in beginning to normalize policy means that the Committee considers it unlikely that economic conditions will warrant an increase in the target range for the federal funds rate for at least the next couple of FOMC meetings," Yellen said in prepared remarks before the Senate Banking Committee
Speaking on investing in Greece, Rubenstein said while he enjoyed visiting the country, but as a place to invest money it is very "risky"
"I think it's not for somebody who really doesn't know a great deal about what they're doing investing in Greece. It's not a place for people that are worried about the widows-and-orphans kind of returns," he said.