President Donald Trump on Thursday threatened to cancel an upcoming meeting with Mexican President Enrique Pena Nieto if his country is unwilling to foot the bill for Trump’s proposed wall on the U.S.-Mexico southern border. “The U.S. has a 60 billion dollar trade deficit with Mexico. It has been a one-sided deal from the beginning of NAFTA with massive numbers of jobs and companies lost,” Trump wrote in a series of tweets from his personal account. “If Mexico is unwilling to pay for the badly needed wall, then it would be better to cancel the upcoming meeting.” The declaration came after Pena Nieto declared that Mexico “does not believe in walls,” and said his country wouldn’t pay for one. On the campaign trail, Trump often cited the trade deficit as a way for Mexico to pay for the wall. Earlier this week, Trump signed executive orders mandating that planning for the construction of the wall start immediately. He said in an interview with ABC News that he expects construction to begin within “months.” The meeting between Trump and Pena Nieto is slated for Jan. 31.