Exxon Mobil Corp. (XOM) extended its partnership with Russia ’s state-controlled oil company even as U.S. and European nations threaten additional sanctions to punish Vladimir Putin’s regime for its actions in Ukraine. Exxon signed the agreement with OAO Rosneft (ROSN) Chief Executive Officer Igor Sechin at a forum in St. Petersburg today, extending a pact that involves drilling for crude in the Arctic and Siberia and liquefying natural gas for export in Russia’s Far East, according to a statement on Moscow-based Rosneft’s website. Exxon didn’t immediately return a phone message seeking comment. Exxon is among American oil producers that rebuffed U.S. State Department pressure to skip the International Economic Forum this week in Putin’s hometown. With at least $30 billion already invested in Russia’s oil and gas sector, U.S. and European explorers are betting the Ukraine crisis won’t derail their aspirations to capture some of Russia’s 75 billion barrels […]