By Stephanie Kelly NEW YORK (Reuters) – Oil prices fell on Sunday at the start of the session, extending last week’s decline, as a U.S. official said Russia was showing signs it might be willing to have substantive negotiations over Ukraine. Brent crude futures fell $1.82, or 1.6%, to $110.85 a barrel by 6:47 p.m. ET (2247 GMT). WTI crude futures fell $2.41, or 2.2%, to $106.92 a barrel. Russia’s invasion of Ukraine in late February, which Moscow calls a “special operation,” has roiled energy markets globally. Brent last week was down 4.8% after hitting $139.13 on March 7. U.S. crude recorded …