(This Feb. 26 story has been refiled to fix the syntax in the headline)

By Niket Nishant

(Reuters) - Warren Buffett-led Berkshire Hathaway's shares closed down by more than 2% on Monday, slowing its march to $1 trillion market value on investor worries after the U.S. government warned of a lawsuit against its power company, PacifiCorp.

Berkshire disclosed the risk of a lawsuit against its unit over its alleged failure to cover $356 million in costs associated with the 2020 Slater wildfire in southern Oregon and northern California.

The investment conglomerate had warned on Saturday that the parent of PacifiCorp and one of Berkshire's biggest businesses outside insurance, Berkshire Hathaway Energy, was under pressure.

"It will be many years until we know the final tally from BHE's forest-fire losses and can intelligently make decisions about the desirability of future investments in vulnerable western states," Buffett wrote in his annual letter to shareholders.

He also toned down expectations for Berkshire's share price, saying it did not have many lucrative investment opportunities left, while reassuring investors that the biggest financial firm by market value was "built to last".

The 93-year-old investing legend told shareholders that Berkshire would perform slightly better than the "average American corporation", but anything beyond that is "wishful thinking", even though it had a cash pile of $167.6 billion.

"There remain only a handful of companies in this country capable of truly moving the needle at Berkshire, and they have been endlessly picked over by us and by others... All in all, we have no possibility of eye-popping performance," Buffett wrote.

TRILLION-DOLLAR MILESTONE

Investors closely watch Berkshire as its results are often seen as a bellwether for the U.S. economy.

"While this reads as if Buffett is saying that global equities are fairly valued, the truth is more nuanced than that," Nicholas Colas, co-founder of DataTrek Research, wrote in a note.

"Berkshire is a huge business and needs to take substantial positions in large companies in order to 'move the needle'. Markets are generally good at pricing those sorts of stocks, hence the lack of opportunities."

Berkshire's annual operating profit climbed 21%, to $37.4 billion on improved underwriting and higher investment income from the insurance segment. Operating profit for the fourth quarter also came in ahead of analysts' expectations.

A $1 trillion market value would put Berkshire among a rarefied list of American businesses, which currently includes tech giants like Microsoft and Apple.

Berkshire's Class A shares dropped 2.16%, while its Class B shares, which carry higher voting rights and whose value is 1/1,500th of Class A shares, slipped 1.94%. That left the conglomerate with a stock market value below $900 billion.

"We continue to believe shares are an attractive stock in an uncertain macro environment," UBS analyst Brian Meredith said.

Buffett in his letter also mourned the passing of his longtime second-in-command Charlie Munger, while assuring investors that vice chairman and designated successor Greg Abel was "ready to be CEO of Berkshire tomorrow".

(Reporting by Niket Nishant, Manya Saini and Jaiveer Singh Shekhawat in Bengaluru and additional reporting by Noel Randewich in San Francisco; Editing by Arun Koyyur and Pooja Desai)