LONG BEACH, Calif. (AP) _ Greenpeace activists unsuccessfully tried to board a tanker filled with a million barrels of crude oil Wednesday, then followed the 900-foot vessel as it made its way toward port.

The Coast Guard joined the convoy to ensure the confrontation didn't end with an oil spill.

``We just want to ensure safety, not only of the vessel but also of the Greenpeace members,'' said Lt. Carlos Mercado, a Coast Guard public affairs officer.

Five activists left Greenpeace's ship, the Arctic Sunrise, on small inflatable boats to meet up with the Pecos, a tanker contracted by British Petroleum Amoco to deliver Argentine oil to a terminal in Long Beach.

The Pecos' deck was too high above the waterline for the activists to board, said Melanie Duchin, a Greenpeace member aboard the Arctic Sunrise.

Three Coast Guard boats kept the activists at least 100 yards from the tanker, Mercado said. The Arctic Sunrise and one Coast Guard boat remained Wednesday evening. Mercado said the activists broke the law by interfering with a ship's passage, but he didn't know if anyone would be charged.

Duchin said Greenpeace wanted to draw attention to the role of fossil fuels in global climate change. The group wants the company to build a $660 million solar-panel factory, saying that such a large-scale facility would dramatically reduce the cost of solar power.

Walter Neil, external affairs manager for British Petroleum's Carson refinery, said the company is the world's largest provider of solar energy and is active in further developing solar power and cleaner burning fuels.

``Energy is our business,'' he said, ``we still need to keep the business running while we search for alternative fuels.''