Washington (CNN) The White House on Sunday decried Democratic-led congressional investigations, saying Democrats are refusing to abide by "rules and norms" that govern oversight authority as they issue subpoenas for documents the Trump administration refuses to hand over.

"There are rules and norms governing congressional oversight of the executive branch, and the Democrats simply refuse to abide by them," White House deputy press secretary Steve Groves said in a statement. "Democrats are demanding documents they know they have no legal right to see -- including confidential communications between the President and foreign leaders and grand jury information that cannot be disclosed under the law."

The White House, Groves said, "will not and cannot comply" with what he called "unlawful demands made by increasingly unhinged and politically-motivated Democrats."

President Donald Trump responded later Sunday to Democrats' accusations of a constitutional crisis.

"The Democrats (sic) new and pathetically untrue sound bite is that we are in a 'Constitutional Crisis,'" Trump tweeted , calling them "a sad JOKE!"