(Bloomberg) ? Shares of Ship Finance International Ltd., an oil-tanker owner that leases vessels to other companies, fell the most in more than 22 months after Citigroup Inc. said the stock may be overvalued.

Shares of Bermuda-based Ship Finance fell $1.17, or 5.3 percent to $21.78 today at 10:50 a.m. in New York, valuing the company at $1.6 billion.

A close at that price would be the biggest one-day decline since January 4, 2005.

Ship Finance's 8.7 percent dividend "might not be sustainable" Citigroup analyst John Kartsonas wrote in a note Friday. He lowered his rating on the stock to "sell" from "hold".

The New York-based analyst also said it was an "improbable scenario" Ship Finance's oil tankers will earn the rates the "market" valuation of the stock implies.

Ship Finance is led by Norwegian billionaire John Fredriksen.

Most of its vessels are leased to Frontline Ltd., the world's biggest oil-tanker operator by capacity. It was spun off from Frontline in June 2004.

Fredriksen, through offshore companies, is the biggest shareholder in both companies.