June 5, 2014 12:51 PM EDT

President Barack Obama came out against Scottish independence on Thursday, voicing support for a unified U.K. as Scotland gears up for a September referendum.

“We obviously have a deep interest in making sure that one of the closest allies that we will ever have remains a strong, robust, united and effective partner,” Obama said in Brussels. “But ultimately these are decisions that are going to be made by the folks there.”

The Scottish electorate will vote on independence on Sept. 18. The Scottish government hadn’t responded to Obama’s comments as of early Thursday afternoon, but at least one former official was surprised that he weighed in.

“I’m surprised that he has stepped into this,” the former U.K. diplomat Lord Malloch-Brown said, according to BBC. “I don’t think it will be very helpful for anybody.”

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