New York's main contract, West Texas Intermediate for delivery in August, jumped 36 cents to $90.97 a barrel in morning trade and Brent North Sea crude also for August rose 25 cents to $106.24.

"Generally, prices are reflective of the economic condition of the world such as the debt issue in Greece," said Shailaja Nair, an analyst with energy information provider Platts.

Greece is expected to grind to a halt on Tuesday as protesters launch a 48-hour general strike against the government which is desperate to push through austerity cuts demanded from lenders to avoid a default.

As parliament votes on the belt-tightening measures to unlock 12 billion euros ($17 billion) of funds from the EU and IMF, unions have called on Greeks facing hefty tax hikes to stage mass demonstrations.

Prime Minister George Papandreou begged the Greek parliament late Monday to do its "patriotic duty" and vote to keep the country "on its feet."

A Greek default risks sparking a financial contagion across the rest of Europe that many fear could affect global financial stability.

Copyright AFP (Agence France-Presse), 2011