Donald Trump disputes departing Defense Secretary Jim Mattis over Russia, China

WASHINGTON – In an extraordinary public battle between a commander-in-chief and defense secretary, President Donald Trump appeared to push back Friday on Pentagon chief Jim Mattis over policy toward Russia and China.

"There has never been a president who has been tougher (but fair) on China or Russia," Trump said on Twitter. "Never, just look at the facts. The Fake News tries so hard to paint the opposite picture."

Trump did not cite Mattis by name, but his latest blame-the-media tweet came the morning after Mattis cited Russia and China in a resignation letter rebuking Trump over his "America First" foreign policy.

More:Defense Secretary Jim Mattis leaving his job after clash with Trump over Syria

Trump's alienation of longtime allies in Europe and Asia are allowing Russia and China to impose themselves on other countries to the detriment of American security," Mattis said.

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"It is clear that China and Russia, for example, want to shape a world consistent with their authoritarian model – gaining veto authority over other nations’ economic, diplomatic, and security decisions – to promote their own interests at the expense of their neighbors, America and our allies," the letter said.

Mattis added: "That is why we must use all the tools of American power to provide for the common defense."

The dispute takes place as special counsel Robert Mueller investigates the president and others over Russian meddling in the 2016 election in an effort to benefit Trump's campaign. Trump has denied any collusion with Russians.

Trump and aides say he has been hard on Russia, citing economic sanctions on the country. As for China, aides noted that Trump is fighting the Chinese over what he calls their unfair trade practices.

Critics, including Mattis, have said other policies benefit the Russians and/or the Chinese. They include Trump's decision this week to withdraw U.S. troops from Syria, and his potential plans to pull some troops out of Afghanistan.

Lawmakers from both parties expressed anxiety over Mattis' departure, describing the Pentagon chief as a restraining influence on Trump.

Senate Republican leader Mitch McConnell of Kentucky said the nation must "maintain a clear-eyed understanding of our friends and foes, and recognize that nations like Russia are among the latter."

He added: “So I was sorry to learn that Secretary Mattis, who shares those clear principles, will soon depart the administration. But I am particularly distressed that he is resigning due to sharp differences with the president on these and other key aspects of America’s global leadership."