Donald Trump may soon be doing the unthinkable: kissing and making up with bitter enemy Leona Helmsley.

On paper, at least.

In a mammoth deal that would see the two adversaries both signing on the dotted line, Trump may sell his interest in the Empire State Building to Helmsley and her partner, Peter Malkin.

Trump and his Japanese partners are longtime owners of the landmark building while Helmsley and Malkin control the property’s long-term leases.

“Trump wanted to get control of the entire building, but he wasn’t able to,” a prominent real-estate source told The Post.

“So now he’s seriously thinking about selling his interest. There are four or five parties interested, although it would make the most sense for Helmsley and Malkin to step in.”

The deal could be worth $65 to $80 million to Trump and the survivors of the late Japanese tycoon Hideki Yokoi, the developer’s original partner.

Trump receives only $2 million in rent from the lease, which has another 66 years to go.

If the brash real-estate tycoon were to make a deal with the Queen of Mean, it would be like an amicable meeting between a snake and a mongoose.

Trump once called Leona “a bully” and “a bitch on wheelswho is driven mostly by a desire to intimidate others.”

And he said the unflappable widow of Harry Helmsley once embarrassed him at one her bashes by screaming at him and his fashion-model date: “How dare you bring that tramp to one of my parties!”

Trump and Malkin declined comment yesterday on a possible deal and Helmsley could not be reached for comment. The identity of the other potential buyers could not be determined.

But real estate sources said a 100 per cent Helmsley-controlled Empire State Building would be a feather in the cap of one of the most despised women power-brokers in city history.

Leona, who served time in prison for a 1989 tax-evasion conviction, was known for her brutal handling of staffers at her hotels, firing and hiring with an iron fist and profane mouth.

The Empire State Building, at Fifth Avenue and 34th Street, is one of the most famous buildings in the world and was cemented in movie history in 1933, when King Kong climbed to the top with Fay Wray.