(Reuters) - Apple failed to convince a U.S. judge to block Samsung Electronics from selling Galaxy smartphones and tablets in the U.S. market, depriving the iPhone and iPad maker of crucial leverage in a global patent battle between the two companies.

In a ruling released late on Friday, U.S. District Judge Lucy Koh in San Jose, California denied Apple's request for a preliminary injunction against Samsung.

The two companies are engaged in a bruising legal battle that includes more than 20 cases in 10 countries as the they jostle for the top spot in the smartphone and tablet markets.

Earlier on Friday, an Australian court extended a halt on sales of Samsung's latest Galaxy tablet in the country by at least a week, as Apple appeals a ruling that had ended the ban.

Apple sued Samsung in the United States in April, saying the South Korean company's Galaxy line of mobile phones and tablets "slavishly" copies the iPhone and iPad.

But on Friday Koh rejected Apple's bid to ban sales of three smartphone models, as well as the Samsung Tab 10.1.

"It is not clear that an injunction on Samsung's accused devices would prevent Apple from being irreparably harmed," Koh wrote.

Apple spokeswoman Kristin Huguet on Friday referred to previous Apple statements about the case, saying that Samsung's "blatant copying is wrong."

Samsung spokesman Jason Kim said Samsung welcomed Koh's opinion. "This ruling confirms our long-held view that Apple's arguments lack merit," Kim said in an email.

Apple could still prevail in the overall lawsuit. But it's inability to win a quick halt to Galaxy sales in the United States comes as the stakes skyrocket in one of the fastest growing consumer electronics markets.

UNDER PRESSURE

Global tablet sales are expected to explode to more than 50 million in 2011. Apple, which has sold more than 30 million iPads so far, is expected to continue to dominate the market in the near term.

Apple's new CEO Tim Cook is under pressure to show he can fill the large shoes of his predecessor, late Silicon Valley titan Steve Jobs. But in his first quarterly result unveiled as permanent CEO, Apple stunned Wall Street, missing expectations for the first time in years.

Analysts said customers held off buying iPhones in the September quarter, waiting for the October launch of the latest iPhone 4S.

But tablets proved a bright spot. The company moved 11.12 million units during the quarter despite attempts by various manufacturers, including Samsung, to capture a slice of the tablet market.

Now Amazon.com has also entered the fray with its Kindle Fire tablet, but Samsung's Galaxy line-up is widely deemed the closest rival in terms of capability and design to the iPad.

Acknowledging the competition, Cook said it was "reasonable to say" none of Apple's rivals have gained any traction, and he expected the tablet market to be bigger than personal computer in the long term.

In her ruling, Koh wrote that for some of the smartphones, "Apple has established a likelihood of success on the merits at trial."

Koh added that Apple would likely prove Samsung infringed one of its tablet patents. However, Apple had not shown that it was likely to overcome Samsung's challenges to the patent's validity, Koh wrote.

Apple must demonstrate both infringement and validity to succeed in its lawsuit.

The case in U.S. District Court, Northern District of California is Apple Inc v. Samsung Electronics Co Ltd et al, 11-1846.

(Reporting by Dan Levine; Editing by Yoko Nishikawa)