President Trump on Sunday pushed back against Democrats who have described Washington as being in a "constitutional crisis" over the White House's refusal to cooperate with congressional follow-up investigations to special counsel Robert Mueller's report.

"The “Constitutional Crisis” is the Democrats refusing to work. Let them start by fixing the mess that their Immigration Laws have caused at the Southern Border," Trump tweeted Sunday evening.

The “Constitutional Crisis” is the Democrats refusing to work. Let them start by fixing the mess that their Immigration Laws have caused at the Southern Border. — Donald J. Trump (@realDonaldTrump) May 12, 2019

The claim came as Trump railed against the Democrats' lack of action.

"When the Mueller Report came out showing NO Collusion with Russia (of course), it was supposed to be over, back to work for the people. But the Dems have gone “nuts,” and it has actually gotten worse! Hope the Republicans win back the House in 2020, or little will get done!" he tweeted.

Trump has insisted his administration will not comply with House and Senate Democrats' subpoenas because he claims they are politically motivated. The White House has said Trump and his campaign were cleared of collusion and wrongdoing in the special counsel's report.

"The Dems have been working overtime to damage me and the Republican Party by issuing over 80 demands for documents and testimonies, and with NO REASON. That's all they want to do - don't care about anything else!" he tweeted Sunday.

However, 750 federal prosecutors recently released a letter stating that Trump obstructed Mueller's investigation, even if it did conclude no illegal action took place during the 2016 election.

Trump's Sunday evening tweet accuses liberal lawmakers of not focusing on other issues, mainly the surge of noncitizen families illegally entering and applying for asylum at ports of entry along the southern border in record-high numbers.

Republicans have called for asylum law changes and legislative fixes to a 2015 court ruling that only allows families in federal custody to be held up to 20 days before being released into the U.S. without having their asylum claims resolved.