US STOCKS-Semis, financials drag Wall St lower

* Berkshire bid for Burlington Northern boosts railroads

* UBS posts qtrly loss; RBS, Lloyds, agree to shake-up

* Morgan Stanley downgrades semis, shares fall

* For up-to-the-minute market news, click [STXNEWS/US]

(Updates to morning trading)

By Rodrigo Campos

NEW YORK, Nov 3 (Reuters) - U.S. stocks fell on Tuesday, weighed by technology and financial shares, as Morgan Stanley downgraded the semiconductor sector and after a shake-up at two big British banks and poor results from Swiss lender UBS.

The market decline came even as Warren Buffett's Berkshire Hathaway agreed to buy Burlington Northern in an acquisition deal that values the railroad company at $34 billion, and is Berkshire's biggest deal ever. Burlington shares surged 28 percent to $97.43.

Financials and technology issues have driven much of the market's recovery, and today's negative developments weighed on sentiment.