The comments come after an unusual round of personal entreaties to Scottish voters from the leaders of BP Plc, the Royal Bank of Scotland and several other large companies. The companies asked voters to maintain the 307-year alliance with England, Northern Ireland and Wales.

Chevron, the tenth-largest oil and gas producer in the United Kingdom, will maintain its operations at three large oil and gas fields off the Scottish coast and move forward on two related exploration projects, no matter how the vote fairs, Watson said in an interview.

Scotland will vote on Thursday whether to leave the nation and become independent, a vote that many polls already show is too-close-to-call.

"We've seen where countries and states have chosen to change and we work to get along with the government in power," said Watson, who became CEO of the California-based company in 2010. "It's a choice for the Scottish people and the people of the U.K."

Indeed, an independent Scotland likely would remain one of Chevron's safer places to operate. The global company works throughout hostile areas in the Middle East and Africa. Earlier this year it pulled expatriate staff out of Iraq's Kurdistan region as Islamic State militants advanced.

Oil tax revenue is seen by many in the pro-independence camp as a prime funding mechanism for any new independent Scottish government, much the way Norway relies heavily on profit from state-controlled oil giant Statoil.

North Sea energy production has been slowly falling for years, though, making reliance on oil tax revenue for large social projects an uncertain prospect. Watson acknowledged that costs are rising globally to find new energy supplies, and he has focused most of Chevron's investments outside the North Sea.

RUSSIA AND UKRAINE

Separately, Watson said Western economic sanctions against Russia likely will do little to hurt that country's energy production, though could harm future projects.

The United States last week barred U.S. companies from selling goods or services to five Russian energy companies for deepwater, Arctic and shale projects.

"My expectations are that Russia will continue to be a major oil and gas producer for many years to come," Watson said after a speech to business leaders in Minnesota. "Sanctions as a foreign policy are often very difficult to put in place."

The sanctions were designed to punish Russia for meddling in Ukraine and annexing Crimea in March.

California-based Chevron signed a $10 billion (6.1 billion pounds) deal last fall to develop Ukraine's Olesska field, estimated to hold enough natural gas to supply the European Union's needs for three years.

The recent turmoil between Ukraine and Russia has put that project on hold. Watson said he has not talked with Ukraine's president, Petro Poroshenko. Ukraine is heavily dependent on Russia for gas.

(Reporting by Ernest Scheyder; Editing by Terry Wade, Bernard Orr)

By Ernest Scheyder