Keeping up the tradition of sitting presidents not publicly weighing in on the selection of their party's next nominee, the White House said Obama would wait until after the Democratic primaries to make his views known.
Asked if Obama would automatically back his former secretary of state, White House spokesman Josh Earnest said "No."
"The president has not offered up any sort of endorsement at this point," said Earnest, despite Obama's glowing words for Clinton on Saturday.
"I think she would be an excellent president," he added.
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To most ears that would sound like a full-throated endorsement.
But the White House and the Democratic Party will be keen to get as much political mileage out of Obama's backing as possible.
Official endorsements play a pivotal role in US electoral politics, with candidates going out of their way to woo would-be supporters -- with promises of plum positions if necessary.
With no more elections to run, Obama may simply seek assurances that Clinton will safeguard key aspects of his legacy.
Once "voters across the country have decided who the Democratic nominees should be, I think that Democratic nominee can be confident that they'll enjoy the support of President Obama and their campaign," said Earnest.