WASHINGTON - Executives from two major oil companies told Congress on Thursday that the U.S. government should open more offshore areas to oil and natural gas drilling so America can rely less on foreign suppliers.

There is some hypocrisy in locking these resources away while relying on resources produced in other countries, said Marvin Odum, the President of Shell Oil Co., the U.S. unit of Royal Dutch Shell Plc.

Instead, we should embrace policies that provide access to our own oil and gas resources, Odum told the Senate Energy and Natural Resources Committee at hearing on offshore energy production.

The U.S. Interior Department is considering a five-year plan that might open new offshore areas to drilling.

But many environmental groups oppose expanded offshore drilling, fearing oil spills could result, especially when energy companies move into the deeper waters of the Gulf of Mexico where platforms are susceptible to hurricanes.

The potentially irreversible effects of oil pollution on marine ecosystems and their dependent economies do not justify the potential short-term economic gains that might accrue from offshore oil and gas development, said Jeffrey Short with the international marine conservation group Oceana.

The industry says improved drilling technology allows oil companies to search for supplies in an environmentally friendly way.

These advances enable more production while reducing environmental impacts and allowing for efficient use of existing facilities and infrastructure, David Rainey, Vice President for Gulf of Mexico Exploration at BP America, the U.S. unit of BP Plc.

Finding oil and gas for the future requires exploring in areas that are ever deeper and more complex, Rainey said.

The executives also said oil and gas supplies will still be needed even while the United States and other countries develop plans to fight global warming and promote use of more renewable energy sources like wind and solar power.

We must stop ignoring the fact that oil and gas will play a major part in meeting America's energy demands for several decades as we transition to a more sustainable energy future, said Shell's Odum.

(Reporting by Tom Doggett; Editing by David Gregorio)