Mexico City - The Mexican government had no immediate reaction to a tweet by US President Donald Trump that appeared aimed at cancelling a planned January 31 meeting with Mexican President Enrique Pena Nieto.Trump tweeted Thursday that "If Mexico is unwilling to pay for the badly needed wall, then it would be better to cancel the upcoming meeting" in Washington DC.Trump said on Wednesday he would start building a US-Mexico border wall and vowed to make Mexico pay for it. Mexico opposes the wall and has repeatedly said it won't pay for it.Mexican officials said there was no immediate reaction to Trump's tweet. Officials said on Wednesday Mexico was "considering" cancelling.Former foreign relations secretary Jorge Castaneda told local media "Pena Nieto has no other choice but to say 'I'm not going.'"Trump's unusual, voluble and unpredictable style appeared to catch Mexico's normally quiet and cautious diplomacy off guard.Finance Secretary Jose Antonio Meade told Grupo Formula radio that "I think that, in general, diplomacy is not conducted via Twitter.""The foreign relations secretary is involved up there, having meetings up there, and we'll have to see what comes out of that, what report they send to the president and what conclusions they arrive at from all that," said Meade.