WASHINGTON (Reuters) -U.S. mortgage rates increased to a four-month high this week and could rise further amid fears that President-elect Donald Trump's proposed economic policies could stoke inflation. The average rate on the popular 30-year fixed-rate mortgage climbed to 6.79%, the highest level since July, from 6.72% last week, mortgage finance agency Freddie Mac said on Thursday. As supply remains below pre-pandemic levels, rising mortgage rates and elevated house prices have combined to stifle sales of previously owned homes, which hit a 14-year low in September.