The summit's "Caracas Declaration" calls for solidarity among OPEC members and emphasizes the need to help poorer nations.
Venezuelan President Hugo Chavez urged fellow leaders to become advocates for developing nations and to join forces in fighting U.N. sanctions against Iraq.
But some remain skeptical about all the talk of cartel unity.
"I think, frankly, that's lip service," said Jareer Elass, managing director of Oil Navigator, a Washington-based consulting firm.
Saudi Arabia, OPEC's largest oil producer, sought to temper the tone struck in the summit declaration by advocating prudence in discussions with industrialized nations.