US President Donald Trump on Monday staunchly backed Mike Pompeo over suggestions he asked a government worker to walk his dog, saying the nation's top diplomat had better things to do.Democrats in Congress have launched an investigation after Trump late on Friday fired the internal watchdog of the State Department, who according to lawmakers was looking in part into a complaint over how Secretary of State Pompeo asked a staffer to carry out personal errands.READ | US Democrats launch probe into ouster of State Dept watchdogQuestioned by reporters, Trump said he did not know Inspector General Steve Linick and fired him at the request of Pompeo, a loyal aide."Here's a man supposed to be negotiating war and peace with major, major countries with weaponry like the world has never seen before," Trump said of Pompeo."And the Democrats and the fake news media, they are interested in a man who is walking their dog," he said."I'd rather have him on the phone with some world leader than have him wash dishes because maybe his wife isn't there."'Obama appointments'Trump said Pompeo might be busy speaking to Chinese President Xi Jinping "about paying us for some of the damage they've caused to the world and us", or to North Korean leader Kim Jong Un."He says, 'Please, can you walk my dog?'" Trump said. "To who, a Secret Service person or somebody, right?"Xi is unlikely to speak by phone to Pompeo rather than Trump, his counterpart, and Kim is not known for telephone diplomacy.Trump, like Pompeo, said he had an "absolute right" to oust Linick - who was appointed by former president Barack Obama - without stating a reason."Many of these people were Obama appointments and I just got rid of them," Trump said.Linick earlier issued a critical report about former Secretary of State Hillary Clinton's use of a personal email account - an issue seized upon in the 2016 election by Trump.