Washington, March 28 : US President Donald Trump on Friday lashed out at General Motors for demanding "top dollars" for manufacturing ventilators that are in short supply to treat COVID-19 patients. In a series of tweets, Trump hit out at General Motors and Ford, directing them to immediately manufacture ventilators. "As usual with "this" General Motors, things just never seem to work out. They said they were going to give us 40,000 much needed Ventilators, "very quickly". Now they are saying it will only be 6000, in late April, and they want top dollar. Always a mess with Mary B. Invoke "P"," Trump said in a tweet referring to GM CEO Mary Barra. General Motors said in a statement that it is partnering with medical device maker Ventec to convert an Indiana GM facility into a ventilator production plant. The companies said they expect the first ventilators will be available next month with the ability to produce more than 10,000 per month after that. "General Motors MUST immediately open their stupidly abandoned Lordstown plant in Ohio, or some other plant, and START MAKING VENTILATORS, NOW!!!!!! FORD, GET GOING ON VENTILATORS, FAST!!!!!!" Trump said in another tweet. Trump added "Invoke 'P'" to the end of one of his Friday tweets, which in another tweet was clarified to be a reference to the Defense Production Act (DPA). The US president last week invoked the DPA, which allows him to compel companies to manufacture critical supplies in times of crisis. "Invoke "P" means Defense Production Act!," Trump added. "We have just purchased many Ventilators from some wonderful companies. Names and numbers will be announced later today!," Trump said. The US has now the highest number of coronavirus patients in the world and ventilators much in demand especially in New York which has the highest number of infected patients in the US. /IANS