By Laila Kearney NEW YORK (Reuters) -Oil prices toggled between negative and positive territory on Friday as hopes of stronger Chinese demand and output cuts by OPEC+ contended with concern about a global economic downturn and the impact of interest rate rises on fuel use. To fight inflation, the U.S. Federal Reserve is trying to slow the economy and will keep raising its short-term rate target, Federal Reserve Bank of Philadelphia President Patrick Harker said on Thursday in comments that weighed on oil. But crude is gaining support from a looming European Union ban on Russian oil, as well as…