Crude-oil futures closed slightly higher Monday after hitting a new record near 120 dollars a barrel as a weekend refinery strike closed a pipeline system that delivers a third of Britain's North Sea oil to its refineries.

Rebel attacks in Nigeria and tension in Persian Gulf also fanned concerns about supply disruptions.

Ira Eckstein is president of Area International Trading Corporation.

"Half of Nigeria's oil is off line right now, over a million barrels a day of light, sweet crude oil that we really can't replace so that's a very big factor, one of the bigger factors in the market right now."

Eckstein explains that a lot will depend on the price of oil. The U.S. dollar has recently held its ground, so the supply side will be a key to future prices, adding that he does not think gasoline prices will keep climbing.

"Unless some more supply gets off the market, that could be the top for now. You know, I think 120 to 123 dollars would be the top."

In Nigeria, workers at an ExxonMobil Corp. joint venture cut production by an unspecified amount to demand more pay. Militant attacks on oil infrastructure have also cut production of Nigeria' s light, sweet crude, which is easily refined.

U.S. crude oil futures rose sharply Friday, lifted by supply disruptions in Nigeria and Britain and news that a ship hired by the U.S. military fired warning shots at approaching boats in the Persian Gulf.