President Obama bluntly challenged the Supreme Court over a pending ruling on the validity of ObamaCare subsidies, complaining Monday that the court should never have taken up the case -- and warning that a ruling against subsidies would be a "twisted interpretation" of the law. 

The president and his administration's legal team for months have fought the Affordable Care Act court challenge, which is over whether people who enrolled through the federal are entitled to subsidies. 

But the president's comments on Monday, during a press conference on the sidelines of the G-7 summit in Germany, were perhaps his toughest to date. He strongly suggested the court would be running afoul of established legal guidance if it rules against the administration, and took the rare step of saying the court should have stayed out of this fight. 

"This should be an easy case. Frankly, it probably shouldn't even have been taken up," Obama said. 

The administration has argued in court that the subsidies are valid through both state-run exchanges and exchanges run through Foes argue that the Affordable Care Act stipulates subsidies are only intended for those buying insurance on state-run exchanges. 

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The court decision, expected any day, could have far-reaching implications because millions would lose their insurance if the court rules against the administration. 

Yet the Obama administration has faced criticism for declining the spell out what its contingency plan is if the court rules that way, instead voicing confidence that the Supreme Court will keep the program as is. 

Obama again voiced that confidence on Monday, and urged the court not to rule otherwise. 

He said it's safe to "assume" the court will do what most legal scholars expect and "play it straight." Obama said it has been well-documented that Congress never intended to exclude people who went through the federal exchange. 

To rule the other way, the president said, would be a "contorted reading of the statute" and a "twisted interpretation." 

But if that does happen, Obama said, "that throws off how that exchange operates" and millions of people would lose subsidies. 

"It's a bad idea," Obama said. 

The president went on to mount a robust defense of the law itself, saying "none" of the alleged "horrors" associated with ObamaCare have "come to pass." 

The Associated Press contributed to this report.