President Trump on Thursday vowed to build a border wall despite White House chief of staff John Kelly’s recent comment that his campaign promise to do so was “not fully informed.”

“The Wall is the Wall, it has never changed or evolved from the first day I conceived of it. Parts will be, of necessity, see through and it was never intended to be built in areas where there is natural protection such as mountains, wastelands or tough rivers or water,” Trump tweeted Thursday morning.