(Reuters) – Amazon Inc is planning to develop its own software for placing advertisements online, The Wall Street Journal reported, citing people with knowledge of the matter. While the in-house platform is initially planned to replace ads supplied by Google Inc on Amazons own website, the new system could challenge Google and Microsoft Corps advertising business in the future, the newspaper cited the people as saying. Amazons system would resemble Googles AdWords, and is planned to make it easier for marketers to reach the companys users, the newspaper reported the people as saying. The retailer is also building a tool that would help advertising agencies buy in bulk for thousands of advertisers, the Journal said, citing the people.