WASHINGTON — President Donald Trump has berated the conservative Koch brothers, tweeting that the billionaire industrialists are a "total joke in real Republican circles" and that he is "a puppet for no one."

It's the latest salvo between the president and Charles and David Koch, who did not endorse Trump in his 2016 presidential bid and have lashed out at Trump's spending plans and trade policies.

On Monday, the political advocacy network created by the billionaire industrialists announced it would not back the GOP candidate in the North Dakota Senate race. The decision was a warning shot to fellow Republicans that they should do more to elect candidates who challenge government spending.

"The globalist Koch Brothers, who have become a total joke in real Republican circles, are against Strong Borders and Powerful Trade," Trump tweeted. "I never sought their support because I don't need their money or bad ideas."

He later added: "I'm for America First & the American Worker — a puppet for no one. Two nice guys with bad ideas."

The outburst marks a new chapter in the strained relationship between the Trump administration and the expanding conservative network created by billionaire industrialists Charles and David Koch, who refused to endorse the Republican president in 2016.

Trump has effectively taken over the modern-day Republican Party on almost every level, even after ignoring long-held conservative beliefs on government spending, free trade and foreign policy.

David H. Koch
Philanthropist and billionaire David H. Koch attends the U.S. Olympic And Paralympic Foundation Event on May 17, 2017 in New York City. Photo by Lars Niki/Getty Images for United States Olympic Committee

Trump has played a role in several Republican primaries, helping candidates in Georgia, Alabama and South Carolina in recent weeks with endorsements that underscore his influence within the GOP.

But the president's policies have been at odds with the Kochs' libertarian political arm, Americans for Prosperity. The group says it still plans to focus its resources on helping Republican Senate candidates in Tennessee, Florida and Wisconsin.

But Charles Koch told reporters in recent days that he cared little for party affiliation and regretted supporting some Republicans in the past who only paid lip service to conservative principles.

Network leaders over the weekend repeatedly lashed out at the Republican-backed $1.3 trillion spending bill adopted in March, which represented the largest government spending plan in history. The Trump White House budget office now predicts that next year's federal deficit will exceed $1 trillion, while reaching a combined $8 trillion over the next 10 years.

The Kochs were equally concerned about the Trump administration's "protectionist" trade policies, which have sparked an international trade war and could trigger a U.S. recession, Koch said.

"We're going to be much stricter if they say they're for the principles we espouse and then they aren't," Koch vowed. "We're going to more directly deal with that and hold people responsible for their commitments."

Colorado-based energy investor Chris Wright, a longtime Koch donor, said the Republican Party may have lost its way in the age of Trump. He and his wife, Liz, encouraged the Koch network to ignore Republican candidates who turn their back on key conservative principles out of loyalty to Trump.

"They don't deserve to be funded if they don't uphold our values," Liz Wright said.