U.S. antitrust regulators gave Google Inc approval to buy mobile advertising rival AdMob, after months of delay and rumor that Google was headed for a court fight with government officials over the transaction.

The Federal Trade Commission said in a statement on Friday that it was concerned that two top mobile advertising networks were combining, but said Apple Inc's entry into the market would mitigate the effects of the Google/AdMob powerhouse.

The decision was a difficult one because the parties (Google and AdMob) currently are the two leading mobile advertising networks, and the commission was concerned about the loss of head-to-head competition between them, the FTC said in a statement.

Google had said in November that it would buy AdMob for $750 million in stock.

During the FTC's review of the merger, Apple acquired the third largest mobile ad network, Quattro Wireless. The commission said on Friday it believed Apple would quickly become a strong mobile advertising network competitor.

Though we have determined not to take action today, the commission will continue to monitor the mobile marketplace to ensure a competitive environment and to protect the interests of consumers, the FTC said.

AdMob Chief Executive Omar Hamoui, who founded the firm, said he was pleased with the decision and would work with Google to close the deal.

Shares of Google were up 1.2 percent to $480.60 in afternoon trade, in line with the rise in the tech-heavy Nasdaq Composite Index.

(Reporting by Diane Bartz; Editing by Tim Dobbyn)

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