President Trump took to Twitter on Monday to blame Democrats for obstructing U.S. ambassadorships.

“Heads of countries are calling wanting to know why Senator Schumer is not approving their otherwise approved Ambassadors!? Likewise in Government lawyers and others are being delayed at a record pace! 360 great and hardworking people are waiting for approval from....,” he tweeted.

He continued: “....Senator Schumer, more than a year longer than any other Administration in history. These are people who have been approved by committees and all others, yet Schumer continues to hold them back from serving their Country! Very Unfair!”

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The office of Senate Democratic Leader Chuck Schumer, D-N.Y., didn’t return a request for comment over the tweets.

Also Monday afternoon, Schumer and Speaker-designate Nancy Pelosi, D-Calif., commented on the partial government shutdown over Trump's demand for $5 billion for the border wall: “While President Trump drags the nation into Week Two of the Trump Shutdown and sits in the White House and tweets, without offering any plan that can pass both chambers of Congress, Democrats are taking action to lead our country out of this mess. This legislation reopens government services, ensures workers get the paychecks they’ve earned and restores certainty to the lives of the American people.”

As the shutdown drags on, pressure is expected to build on all sides for a resolution, as public parks and museums close, and some 800,000 federal workers are going without pay.

The president continued to insist Monday he wants to build a wall along the U.S.-Mexico border.

Trump tweeted Monday night, "The Democrats will probably submit a Bill, being cute as always, which gives everything away but gives NOTHING to Border Security, namely the Wall."

He added: "...Remember this. Throughout the ages some things NEVER get better and NEVER change. You have Walls and you have Wheels. It was ALWAYS that way and it will ALWAYS be that way! Please explain to the Democrats that there can NEVER be a replacement for a good old fashioned WALL!"

There has been little contact between the White House and congressional Democrats for more than a week, other than the Republican president's Twitter barbs, as the two parties remain divided over his insistence on funding for a wall along the U.S.-Mexico border.

One Democrat who did clap back at Trump’s ambassadorships tweet was Sen. Chris Murphy, D-Conn.

"This is a lie. Because: a. The problem isn’t a long list of unapproved ambassadors. It’s that Trump left the most important slots vacant for virtually his entire first 2 years (eg Saudi Arabia) b. Ambassadors need only 50 votes. Mitch, not Chuck, is the issue," Murphy tweeted, referencing Senate Majority Leader Mitch McConnell, R-Ky.

"Re Trump’s rant on non-existent 'unapproved' Ambassadors: For 2 years, Trump refused to appoint an Ambassador to Saudi Arabia. Both the King and [Saudi Crown Prince Mohammed bin Salman] refuse to meet w anyone below an Ambassdor. So during entire Yemen & Khashoggi crisis, our embassy was virtually powerless," he added.

Trump announced in the middle of November that he was nominating John Abizaid, the longest-serving commander of the U.S. Central Command and a retired four-star general, to be U.S. ambassador to Saudi Arabia, filling a key diplomatic vacancy at a time when U.S.-Saudi relations are being tested by the slaying of a journalist critical of the Saudi royal family..

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It’s a post that has been empty since former ambassador Joseph Westphal left in January 2017.

If confirmed by the Senate, Abizaid would become ambassador as the Trump administration is weighing the U.S. response to the killing of Washington Post contributor and activist Jamal Khashoggi at the Saudi Consulate in Istanbul.

Turkish officials claimed Khashoggi was killed by a 15-member assassination squad sent from Riyadh on orders from the highest levels of the Saudi government.

The Associated Press contributed to this report.