The NATO Secretary General, Javier Solana, says Greece and Turkey have agreed on a series of measures to ease tensions on the Aegean Sea and in international airspace.
The countries have numerous territorital disputes in the area, and in 1996 came close to military conflict over the ownership of uninhabited islands in the Aegean.
The deal is based on an agreement the countries signed in 1988.
Mr Solana called the new agreement an important interim result.
The countries are to continue talks on confidence-building measures.
From the newsroom of the BBC World Service