While Hillary Clinton and Barack Obama opted for cordiality in the face of Donald Trump's presidential win, Bernie Sanders' first comments following the results came as a warning to the future president of the United States.

The Vermont senator, who chose to support Clinton after he lost the Democratic nomination to her, echoed his own political campaign message pushing for policies that will restore the "declining middle class" and keep jobs within the country.

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US senator Bernie Sanders said Donald Trump won by tapping into the anger of the declining middle class Justin Sullivan/ Getty Images

"Donald Trump tapped into the anger of a declining middle class that is sick and tired of establishment economics, establishment politics, and the establishment media," Sanders said in his 9 November statement.

"People are tired of working longer hours for lower wages, of seeing decent paying jobs go to China and other low-wage countries, of billionaires not paying any federal income taxes, and of not being able to afford a college education for their kids — all while the very rich become much richer."

The 75-year-old went on to assure support of a Trump government if it works to improve the conditions of the working class.

"To the degree that Mr Trump is serious about pursuing policies that improve the lives of working families in this country, I and other progressives are prepared to work with him. To the degree that he pursues racist, sexist, xenophobic, and anti-environment policies, we will vigorously oppose him," he concluded.

Ironically, the five states that Sanders won in the primaries — Indiana, Michigan, Oklahoma, West Virginia, and Wisconsin — were also areas where Trump did surprisingly well.