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NEW YORK, Jan 21 (Reuters) - Bond investors mostly shrugged off the second day of a government shutdown in the United States on Sunday, with prices of U.S. Treasury debt futures easing as the market bet that the political impasse would be brief.

Democrats and Republicans, locked in a bitter dispute over immigration, failed to agree on a last-minute deal to fund government operations, causing a shutdown at midnight on Friday. Moderate senators from both parties held talks on Sunday to broker a deal.

U.S. Treasury debt futures prices fell 0.1 percent, or 2/32 in price, indicating the yield in the cash market was set to rise.

Benchmark yields had hit a three-year peak on Friday as the government shutdown loomed.

"The perception is they will come to their senses and do something here," Tim Ghriskey, chief investment strategist at Inverness Counsel, said in reference to U.S. politicians. Inverness is an investment advisory firm in New York.

But "there's certainly reason to become concerned" if the shutdown lasts for more than a week, Ghriskey said.

In the uncertain environment, U.S. bond yields are expected to climb higher, so investors should sell bonds, he said, adding he did not expect the shutdown to cause prices of U.S bonds or stocks to move sharply. (Reporting by Koh Gui Qing and Megan Davies; Editing by Daniel Wallis and Peter Cooney)