Donald Trump has suggested sending the US Army over the border into Mexico to wage war" on drug cartels in a typically bombastic tweet. The US president said his country stood "ready, willing & able to get involved and do the job quickly and effectively" if his Mexican counterpart, Andres Manuel Lopez Obrador, asked him for help. Mr Lopez Obrador declined the offer during a press conference on Tuesday. Mr Trump's suggestion came after an American family was slaughtered by gunmen during an ambush in Mexico's Sonora state. The family had been traveling in a convoy of SUVs. Mr Trump has long used the threat of violent crime within Mexico for political ends, blaming the US neighbour for "sending" rapists and murderers north over their shared frontier. The rhetoric has underpinned his stringent migration policies and border strategy. In a press conference on Tuesday, Mr Lopez Obrador said: "I haven't seen the message from President Trump, but I am sure that it comes from a desire to help, to cooperate, that it has not been disrespectful nor interfering. Every time we speak, it is with that desire to help, and the government respects that greatly. We are very grateful to President Trump - to any foreign government which wants to help - but in these cases we have to act independently and according to our constitution, and in line with our tradition of independence and sovereignty." He did not want to see a war break out, he said. "War is synonymous with irrationality. We are for peace."