Under fire from Democrats ahead of a key budget battle this week, President Trump lashed out on Twitter that a border wall will help stop drugs and gang members from getting into the U.S.

The tweet on Sunday comes as Democrats appear to be digging in their heels against providing funding for the wall in a spending bill needed to fund the government, which runs out of money on April 28. Democratic House Minority Leader Nancy Pelosi said Sunday on "Meet the Press" that a wall is a "sign of weakness."

Trump responded on Twitter on Sunday that the wall is needed to help secure the U.S.-Mexican border.

"The Democrats don't want money from budget going to border wall despite the fact that it will stop drugs and very bad MS 13 gang members," he tweeted.

Trump then tweeted a few minutes later that he isn't going back on his campaign promise that Mexico is going to pay for the wall. Democrats have chided Trump by saying that no taxpayer money should go towards it because of that promise.

Eventually, but at a later date so we can get started early, Mexico will be paying, in some form, for the badly needed border wall. — Donald J. Trump (@realDonaldTrump) April 23, 2017



"Eventually, but at a later date so we can get started early, Mexico will be paying, in some form, for the badly needed wall," he tweeted.