President Obama tweeted out his support for a united Great Britain Wednesday night on the eve of Scotland’s independence referendum.

The referendum — on whether Scotland should separate from the United Kingdom — gets underway Thursday. The latest opinion polls show opponents of separation with a thin lead.

Voters will be asked on Thursday to answer “Yes” or “No” to the question: “Should Scotland be an independent country?”

Obama’s tweet — under his own initials — said “The UK is an extraordinary partner for America and a force for good in an unstable world. I hope it remains strong, robust and united. -bo”

Earlier this week, White House Press Secretary Josh Earnest said the vote is a “decision for the people of Scotland to make.” He said he that while the White House respects “their right to cast their own ballot without interference from people on the outside,” the president believes the United States has “an interest in seeing the United Kingdom remain strong, robust, united and an effective partner.”

Click here to see the complete graphic about what could happen if Scotland votes ‘Yes.’ (Graphic: Bonnie Berkowitz, Kevin Schaul and Gene Thorp – The Washington Post)