"We are substantially subsidizing the militaries of many VERY rich countries all over the world, while at the same time these countries take total advantage of the US, and our TAXPAYERS, on trade. General Mattis did not see this as a problem," Trump said. "I DO, and it is being fixed!"
The comment was made after on Thursday, Mattis in a resignation letter said he was stepping down at the end of February citing the fact that Trump needed to find a defence chief whose views were more aligned with his own.
"To those few senators who think I don’t like or appreciate being allied with other countries, they are wrong, I DO," Trump said. "What I don’t like, however, is when many of these same countries take advantage of their friendship with the United States, both in military protection and trade."
READ MORE: Pentagon Chief Mattis Reportedly Learned He Would Be Fired From Pompeo
Mattis' resignation came a day after the White House said the United States was withdrawing troops from Syria, the plans which the outgoing defence chief has previously slammed as a "strategic blunder."
READ MORE: Shanahan to Become Acting US Defence Secretary After Mattis Resignation — Trump
Border Wall
US President Donald Trump has touched upon the issue of the border wall, which led to the closure of one-quarter of the US federal government.
"Virtually every Democrat we are dealing with today strongly supported a border wall or fence," Trump stated. "It was only when I made it an important part of my campaign, because people and drugs were pouring into our country unchecked, that they turned against it."
Trump was apparently referring to Democratic support for the Secure Fence Act of 2006, which funded 650 miles of steel fence along the border, about half the distance of about 1,100-mile long wall Trump administration officials say will be needed to secure the Southern US border. Natural barriers such as cliffs and mountains would protect the rest of the 1,950-mile boundary.
READ MORE: 'Like in Berlin?': Trump's Call for 'Good Old-Fashioned Wall' Sets Twitter Afire
Senate Democratic leader Chuck Schumer voted for the Secure Fence Act, which passed the Senate on an 80-19 vote. Schumer now refuses to fund Trump’s border wall, claiming that such a barrier would be ineffective halting illegal migration and drug trafficking into the United States.
READ MORE: Alyssa Milano Attacks Veteran's Border Wall Crowdfunding, Gets Slammed
The standoff between Trump and Senate Democrats led to the closure of about one-quarter of the US federal government on midnight Friday, and with most of Congress out of town for the Christmas holiday, lawmakers say there is little prospect of ending the dispute until after the new year.
READ MORE: Twitter Explodes as Trump Unveils PHOTO of 'Beautiful and Effective' Border Wall
Later in the day, White House spokeswoman Sarah Huckabee Sanders stated that US President Donald Trump would meet with Department of Homeland Security (DHS) Secretary Kirstjen Nielsen and other DHS officials to discuss border security.
"The President will meet with Secretary Nielsen and other DHS officials today at 2pm to discuss border security," Sanders said in the statement.
The US Senate will reconvene on Thursday afternoon to continue negotiating a spending bill that will satisfy Trump and Senate Democrats.
