An ordinary, long-scheduled journey of an oil drilling rig into Arctic waters is turning into a major political exercise, attracting international scrutiny and creating a dilemma for Exxon Mobil Corp. Exxon, the top U.S. oil major and the world's most valued oil company, is bringing the rig, called West Alpha, from Norway to the Russian Arctic. It is hoping for a major discovery in the Kara Sea with Russian partner Rosneft Oil Co. The journey has begun just as the United States has slapped the toughest sanctions yet on Russia, including on Rosneft, over escalating violence in Ukraine. Further sanctions are likely after the downing of a Malaysia Airlines' plane in eastern Ukraine.