BRADLEY KLAPPERTROMSO, Norway (AP) â¿¿ U.S. Secretary of State Hillary Rodham Clinton is trekking north of the Arctic Circle, a region that could become a new international battleground for resources. Clinton's trip Saturday to the northern Norwegian city of Tromso is her second to the area in a year. She is bringing a message of cooperation to one of the world's last frontiers of unexplored oil, gas and mineral deposits and underscoring the region's rising significance as melting icecaps accelerate the opening of new shipping routes, fishing stocks and drilling opportunities. To safely exploit the riches, the U.S. and other countries near the North Pole are trying to work together to combat harmful climate change, settling territorial disputes and preventing oil spills. "From a strategic standpoint, the Arctic has an increasing geopolitical importance as countries vie to protect their rights and extend their influence," Clinton said Friday in the Norwegian capital of Oslo. Governments should "agree on what would be, in effect, the rules of the road in the Arctic, so new developments are economically sustainable and environmentally responsible toward future generations." At the least, the U.S. and the other Arctic nations hope to avoid a confrontational race for resources. Officials say the picture looks more promising than five years ago when Russia staked its claim to supremacy in the Arctic and its $9 trillion in estimated oil reserves by planting a titanium flag on the ocean floor. The United States does not recognize the Russian assertion and has its own claims, along with Denmark, Norway and Canada, while companies from Exxon Mobil Corp. to Royal Dutch Shell PLC want to get in on the action. China also is keeping a close eye on the region. Moscow has eased tensions somewhat by promising to press any claims through an agreed United Nations process. But Washington, for its part, has yet to ratify the global body's 1982 Law of the Sea treaty regulating the ocean's use for military, transportation and mineral extraction purposes.