Greece is heading for default, or at least a devaluation, and European Union (EU) leaders have to adopt a plan B to stem contagion to the rest of the bloc, billionaire investor George Soros said on Tuesday.

Greece is heading toward disorderly default and/or devaluation ... A Greek default may be inevitable but it need not be disorderly, he wrote in an editorial for the Financial Times.

While some contagion ... will be unavoidable, the rest of the euro zone needs to be ringfenced. That means strengthening the euro zone, probably by wider use of Eurobonds and a euro zone deposit insurance scheme, he said.

He also reiterated his call for European policymakers to come up with a plan B to muster the political support needed to take such measures and said that Europe's elite had to revert to the principles that guided the union's creation.

Soros, famous for making $1 billion by betting against the British pound in 1992, said in June that it was probably inevitable that a country would exit the euro without naming a specific country.

At a Monday meeting in Brussels, euro zone finance ministers stressed their determination to resist contagion by examining how to help Greece but declined to rule out the possibility of a selective default by the country.

(Reporting by Brenda Goh; Editing by Carol Bishopric)