Arctic oil spill would challenge US Coast Guard

* "No way" to duplicate resources used in BP Gulf spill

* U.S. has one icebreaker ship; China builds a big one

* Coast Guard commandant urges ratifying Law of the Sea

By Deborah Zabarenko, Environment Correspondent

WASHINGTON, June 20 (Reuters) - A major offshore Arctic oil spill could severely challenge the U.S. Coast Guard, with no available infrastructure to base rescue and clean-up operations, the Coast Guard commandant said on Monday.

"There is nothing up there to operate from at present and we're really starting from ground zero," said Adm. Robert Papp Jr. "Now's the time to be not just talking about it, but acting about it."

Several major oil companies, notably Royal Dutch Shell (RDSa.L: Quote), have acquired leases to drill in the Beaufort and Chukchi seas off Alaska. Arctic waters are likely to be accessible to humans for longer periods as the planet heats up.

In May, the extent of Arctic ice was the third-smallest since satellites began collecting data in 1979, according to the U.S. National Snow and Ice Data Center.

Noting that the Coast Guard sent 3,000 people to work on the 2010 BP oil spill in the Gulf of Mexico, Papp told reporters at a government symposium on shrinking Arctic ice: "No way we could deploy several thousand people as we did in the Deepwater Horizon spill."