A storied Fifth Avenue mansion and a sprawling Park Avenue penthouse will soon hit the market—- part of a worldwide portfolio of high-end properties owned by the former Yugoslavia, and worth hundreds of millions of dollars.

Last week, the leaders of five of the republics that used to make up the splintered nation finally agreed to sell off the remaining 51 properties acquired by strongman Josip Broz Tito, Yugoslavia’s postwar dictator who ruled until his death in 1980.

Among the valuable real estate is 854 Fifth Ave., a Gilded Age mansion once occupied by Vanderbilt family heiress Emily Thorn Vanderbilt Sloane, that became the seat of the Yugoslavian mission to the UN.

A six-bedroom, four bathroom duplex apartment at 730 Park Ave. will also go on sale, according to the agreement signed last week by the leaders of Croatia, Serbia, Macedonia, Bosnia and Slovenia.

Appraisals have already been completed on the two properties, which are both in a state of disrepair, a source told The Post.

The Park Avenue co-op, valued at more than $20 million, has been empty since 1992 — a symbol of the collateral damage from the bitter fighting among the successor states.

The Yugoslav government purchased the residence in 1975 for $100,000.

In 2011, The Post exclusively toured the apartment and reported that the five republics had all laid claim to the residence, once occupied by Yugoslavia’s ambassadors to the UN and Tito on his trips to New York.

For 24 years, Serbia has been paying the maintenance costs on the dust-filled 2,325-square foot residence. Maintenance is currently more than $14,000 per month, according to Serbian press reports.

At the Park Avenue building, where neighbors include Conde Nast co-owner Donald Newhouse, any potential purchaser would have to be prepared to spend four years renovating the dilapidated apartment. The building’s strict rules only allow construction in the summer.

The six-story beaux arts mansion on Fifth Avenue, between 66th and 67th Streets, now houses Serbia’s Permanent Mission to the UN.

Upon its completion in 1903, the 3,650-square foot building boasted two elevators, eight bathrooms and 32 rooms. It suffered heavy damage to its first floor when a bomb was tossed into its basement stairwell in the summer of 1975.

In recent years, homes of similar size on Fifth Avenue’s Gold Coast, between East 60th and 85th Streets, have been listed between $28 million and $36 million.

Serbia will receive nearly 40 per cent of the proceeds from the sale of the New York properties, largely because it has maintained both of them for decades, Serbian press reports said last week.

Repeated calls and emails to Serbia’s Permanent Mission to the UN were not returned last week.