Silicon Valley real estate mogul Carl Berg said Sunday that the $1.8 billion deal to sell his portfolio of buildings has fallen apart, a victim of the credit crisis rocking the financial world.

In a tangible sign that the crisis crippling the housing market is spreading to commercial real estate, Berg said the buyer, whom he refused to identify, simply could not obtain a loan to buy Berg’s 6.9 million-square-foot portfolio.

Sunday, after almost three months of negotiations, Mission West Properties agreed to release the buyer from its commitment. Sources speculated the would-be buyer was Starwood Capital Group of Greenwich, Conn., but Berg would not confirm that.

The collapse of valley land mogul Carl Berg’s deal to sell his Mission West Properties portfolio is simply a case of bad timing, say industry experts who predict his “extremely attractive” real estate will find a buyer once the markets settle.Berg announced Sunday the deal to sell his almost 7 million-square-foot portfolio for $1.8 billion fell apart after a bank pulled the loan from the buyer, believed to be Starwood Capital Group of Greenwich, Conn. The deal, in play since the end of May, was caught in the credit crunch triggered by the meltdown of the residential sub-prime markets.