By JOSH LEDERMAN, Associated Press

WASHINGTON (AP) — Former President Barack Obama waded into France's closely watched presidential election on Thursday, offering centrist candidate Emmanuel Macron his best wishes — and even a bit of campaign advice.

In a phone call three days before France's first round of voting, Obama stopped short of an official endorsement as he wished Macron "good luck." Drawing on his own political expertise, he urged the upstart candidate not to take anything for granted.

"Make sure that, as you said, you work hard all the way through," Obama said. "Because you never know, it might be that last day of campaigning that makes all the difference."

Replied Macron, "I will do my best, believe me." Speaking in English, he vowed to "fight to the last minute" and said he'd "keep in touch" with the former U.S. president.

Obama's office announced the call in a short statement. It stressed that Obama wasn't formally endorsing any candidate in the race.

But Macron's team released a video recording on Twitter of Macron talking to Obama on speakerphone. Obama's voice could be heard on the other end. It was a highly unusual move as conversations among politicians are usually kept private.

It was unclear if Macron received permission to release the recording of parts of the call. An Obama spokesman wouldn't say if Obama or his aides authorized Macron to release it.

Macron faces off against anti-establishment populists and other candidates in a first-round vote Sunday. The outcome is being closely watched for signs that Europe is moving toward nationalist candidates who advocate the European Union's dissolution. The top two candidates will progress to a winner-takes-all May 7 runoff.

A victory for Macron would be a vote of confidence in France staying in the EU. Obama, when he was in office, encouraged Britain not to leave the EU, though it ultimately voted to do so anyway.

Obama has stayed almost entirely out of public view since leaving office January 20, declining to weigh in on political issues with a few exceptions. The former president has spent most of his time on a series of beachside vacations with his wife. He is also working on a book and on developing his presidential library and center.

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Reach Josh Lederman on Twitter at http://twitter.com/joshledermanAP