JERUSALEM, Feb 27 (Reuters) - U.S.-Israeli cyber security startup Wiz said on Monday it raised $300 million in a private financing round that takes the firm's valuation to $10 billion, but also said it wouldn't move any of the money to Israel while there is uncertainty about the judicial system.

Plans by Prime Minister Benjamin Netanyahu to overhaul the judicial system, which have sparked nationwide protests on a scale Israel hasn't seen in years, would give the government greater sway on selecting judges while limiting the Supreme Court's power to strike down legislation.

Businesses and economists say the planned reforms could harm Israel as an investment destination. For Israel's tech companies, an independent legal system is crucial to protecting their main asset, intellectual property, with some local tech executives saying they may consider domiciling abroad as a result of the government's plans.

"Unfortunately, due to the legal coup the money raised will not enter Israel," Wiz co-founder and CEO Assaf Rappaport said in a statement. "Our big concern about Israeli high tech is not only about money leaving Israel but also the large amount of money that will no longer enter Israel."

Wiz has already moved tens of millions of dollars of funds out of Israel, sources have said.

Since its founding nearly three years ago, Wiz, which focuses on cloud security and has 650 employees globally, has raised $900 million from investors, including Sequoia Capital, Insight Partners, Blackstone and G Squared.

The latest late stage round was led by Lightspeed Venture Partners and existing investors Greenoaks Capital Partners and Index Ventures.

Citing data from Pitchbook, Wiz said it became the fastest tech firm to reach a $10 billion valuation, ahead of giants such as Uber and Facebook.

"Wiz has been successful until today thanks to an amazing ecosystem that exists in Israel but it is currently facing existential danger," said Rappaport, calling on the government to come up with a compromise that is acceptable to all parties.

Wiz, whose customer base is 35% of Fortune 100 companies, also said it plans to open new offices in the United States in Austin, Dallas and Washington D.C. (Reporting by Steven Scheer Editing by Ari Rabinovitch and Susan Fenton)