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By Kristina Cooke

NEW YORK, April 18 (Reuters) - U.S. stocks surged on Friday as Internet leader Google and heavy equipment maker Caterpillar showed resilience in the face of a slowing economy with profits that defied Wall Street's modest expectations.

Citigroup also fueled a rally that pushed the Dow to its best week since February as investors took comfort that the No. 1 U.S. bank is taking aggressive steps to resolve credit problems that led to its latest quarterly loss, fueling hopes that the credit crisis is near an end.

All three major indexes ended the week up more than 4 percent.

The week was highlighted by a strong showing from Caterpillar, Google and other companies that generate a large part of their profits overseas. The results helped investors overcome persistent fears about the impact of a devastating credit crisis on business and consumer spending.

Shares of Caterpillar, a manufacturing bellwether, rose more than 8 percent after the company reported stronger-than-expected profits.

In technology, Google shares rose 20 percent to $539.41 on the Nasdaq after the company posted results that quashed fears of a slowdown in online advertising as it said it saw no impact from the weakening U.S. economy.

"What we're seeing in the market today is really a microcosm of what we've seen all week," said Subodh Kumar, chief investment strategist, Subodh Kumar & Associates in Toronto. "The market is prepared to reward companies that are showing strong earnings."