A U.N. treaty governing the oceans could clear the way for U.S. oil companies to tap deep oil and gas reserves offshore, which supporters say would bolster America's energy security. But that access might be blocked, because conservatives opposed to the multinational treaty are fighting hard to keep a strong Senate majority from ratifying the pact. When Secretary of State Condoleeza Rice called in January for prompt ratification of the treaty, she gave American oil companies their best hope yet to tap oil and gas reserves lying under thousands of feet of seawater. <snip>.......... In 2003, about 62 percent of...