Berkshire's announcement also shaved more than 3.3% off planemaker Boeing Co's shares. The S&P 1500 airlines sub-index plunged 8% and was on track for its worst day in more than a month.

Berkshire itself posted a record loss of nearly $50 billion, sending its shares down 3% and weighing heavily on the financials sector.

Analysts also said Buffett's relatively bleak reading of the market had hit home with investors.

"The fact that he had sold airline stocks was perhaps a realization that he sees a slow recovery for the economy for a while at least," said James Ragan, director of Wealth Management Research at D.A. Davidson in Seattle.

Nine of the major 11 S&P 500 sectors were trading lower, also pressured by comments from US Secretary of State Mike Pompeo that there was "a significant amount of evidence" the new coronavirus emerged from a Chinese laboratory. An editorial in China's Global Times said he was "bluffing".

All three major stock indexes clawed back more than 11% in April, but the rally is likely to be tested in the coming weeks with investors trying to gauge the pace of an economic recovery as states start emerging from lockdowns.

Data on Monday showed new orders for US-made goods fell more than expected in March and could sink further as the health crisis upends supply chains and exports.

At 11:21 a.m. ET the Dow Jones Industrial Average was down 207.46 points, or 0.87%, at 23,516.23, and the S&P 500 was down 11.45 points, or 0.40%, at 2,819.26.

However, the Nasdaq Composite was up 35.66 points, or 0.41%, at 8,640.61, with heavyweights Microsoft Corp and Amazon.com Inc, seen less disrupted by the pandemic, leading the advance.

With more than half of the S&P 500 companies having reported results so far, analysts now see first-quarter S&P 500 earnings falling 12.5% from a year earlier, and an even sharper 39% decline for the second quarter.

Tyson Foods Inc tumbled 7.9% as the company said it would temporarily close plants as needed and expects meat sales to fall in the second half of the year as shutdowns hammer restaurants and other food outlets.

Declining issues outnumbered advancers for a 2.24-to-1 ratio on the NYSE and a 1.48-to-1 ratio on the Nasdaq.

The S&P index recorded no new 52-week highs and three new lows, while the Nasdaq recorded 12 new highs and 10 new lows.