President Joe Biden has been rumored to be interested in buying Olivia Newton-John 's California ranch ...

however, those who were close to the late star aren't sold on the gossip. A rep for the late "Grease" actress' family tells TMZ ..

. this rumor is "not true," even though a report in the Montecito Journal claimed the President and First Lady Jill Biden were eyeing the property as their post-White House pad. We wouldn't be surprised if the Bidens were taken with the estate, as the sunny abode is located in Santa Ynez .

.. a lush community outside Santa Barbara, known for its world-class wineries.

The outlet claimed POTUS and FLOTUS were set to spend nearly $9 million on the manse ...

which sits along the Santa Ynez River and boasts over 12 acres of land. Still, it seems this report has turned like a bottle of red wine, with Carey Kendall , the Newton-John family's real estate agent, telling TMZ ..

. no one from the Biden family or the President's camp has toured the ranch -- ever!!! Kendall reiterates the rep's denial, noting the rumors have been circulating for a few weeks now. Biden's term in the White House comes to a close on Inauguration Day, when either Kamala Harris or Donald Trump is sworn in as the next Commander-in-Chief.

Looks like we may have to wait until then to learn of the Bidens' post-West Wing plans. We've reached out to Biden's reps for comment ..

. so far, no word back..