LONDON—Oil prices rose slightly on Monday as fresh diplomatic efforts to resolve the Ukraine crisis provided some relief from supply concerns that have kept oil prices near $100 a barrel. Brent crude futures rose 25 cents, or 0.3 percent, to $93.79 a barrel at 1000 GMT. U.S. West Texas Intermediate (WTI) crude futures rose 35 cents, or 0.4 percent, to $91.42 a barrel. French President Emmanuel Macron said on Monday that President Joe Biden and Russian President Vladimir Putin have agreed in principle to a summit over Ukraine but the Kremlin said there were no immediate plans for a meeting. U.S. markets will be closed on Monday for the Presidents Day holiday. “A potential reduction of Ukraine tensions … has seen some sellers emerge in oil in Asia,” OANDA analyst Jeffrey Halley said. European Commission President Ursula von der Leyen said Russia would be cut off from international financial markets …