** Shares of U.S. oil and gas companies rise in premarket trade, tracking crude oil prices O/R

** Brent crude LCOc1 rises 5.1% to $78.04/bbl and U.S. WTI rises 5.2% to $74.16/bbl

** Prices jump U.S. President Donald Trump said the memorandum of understanding to end the conflict with Iran was "over", renewing fears of disruptions to Middle East oil supplies

** Speaking ahead of a NATO summit in Ankara, Trump said the interim pact to end the U.S.-Israel war against Iran was "over", adding he didn't want to engage with Tehran

** Energy majors Exxon Mobil XOM.N and Chevron CVX.N up ~3% and 2.6%, respectively

** Shares of ConocoPhillips COP.N, APA Corp APA.O and Devon Energy DVN.N up between 2.3% and 2.9%

** Oilfield services providers: Baker Hughes BKR.O up ~1%, SLB SLB.N up 1.5% and Halliburton up 2.2%

** Refiners Phillips 66 PSX.N and Marathon Petroleum up over 1%; Valero Energy gains 2.2%

** Separately, Exxon Mobil on Wednesday signaled higher oil prices could boost upstream profit in Q2 by about $5 billion compared to the last quarter