(Reuters) - President Barack Obama will hold a "town hall" meeting on the U.S. economy and jobs on July 6, the White House said on Thursday, but it will be in the virtual world of Twitter, not a brick and mortar building.The White House used Twitter to announce the event on Thursday and invite potential participants to submit questions.The White House Twitter account, which has 2.2 million followers, invited questions to a new account "@townhall" marked with the hashtag "AskObama."Americans' pessimism about the sluggish U.S. economy, especially the 9.1 percent jobless rate, may be the biggest obstacle to Obama's hopes of winning re-election next year.Republicans have criticized the Democratic president as having given too little attention to the country's financial problems while focusing on issues such as his healthcare law.Shortly after the announcement, questions were coming in on topics including green jobs, innovation and corporations for the event, set for 2 p.m. EDT (1800 GMT) on July 6.Obama's White House makes regular use of social media, which it sees as a way to get its message to a wide range of Americans. Obama's Twitter feed, on which he has recently started to write the occasional Tweet himself, is one of the most popular on the system, with 8.9 million followers.(Reporting by Patricia Zengerle)