SAN FRANCISCO (CBS SF) – With the clock ticking toward California’s presidential primary, Gov. Jerry Brown Tuesday announced he was backing Hillary Clinton for the Democratic nomination.

In an open letter published online and on social media, Brown says Clinton has the best shot at stopping Republican Donald Trump, whose candidacy he calls “dangerous.”

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“Donald Trump, has called climate change a “hoax” and said he will tear up the Paris Climate Agreement,” Brown wrote. “He has promised to deport millions of immigrants and ominously suggested that other countries may need the nuclear bomb. He has also pledged to pack the Supreme Court with only those who please the extreme right.”

While supporting Clinton, Brown was also complementary to Sen. Bernie Sanders.

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“I have closely watched the primaries and am deeply impressed with how well Bernie Sanders has done,” he wrote. “He has driven home the message that the top one percent has unfairly captured way too much of America’s wealth, leaving the majority of people far behind. In 1992, I attempted a similar campaign.”

Brown said the stakes were too high in this election for Democrats to keep fighting among themselves.

“Our country faces an existential threat from climate change and the spread of nuclear weapons,” he said. “A new cold war is on the horizon. This is no time for Democrats to keep fighting each other. The general election has already begun.”

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“Hillary Clinton, with her long experience, especially as Secretary of State, has a firm grasp of the issues and will be prepared to lead our country on day one,” Brown wrote. “Next January, I want to be sure that it is Hillary Clinton who takes the oath of office, not Donald Trump.”