The national average price Americans pay to gas up rose 0.4 cent overnight to a record $3.603 a gallon, according to a survey of stations by AAA and the Oil Price Information Service.

While prices are 66 cents higher than a year ago, their rate of increase has slowed some since last week, when prices jumped more than 2 cents a day several times.

Nationally, AAA said, gas was up Monday from $3.28 a month ago and $2.94 a year ago.

Diesel fuel was averaging $4.24 a gallon nationally.

Gas prices are rising in part because refiners are making the seasonal switch-over from making winter-grade gasoline to the more expensive, but less polluting, fuel they must sell during the summer. Supplies tend to fall while refiners are doing this as they try to sell off all of their winter gasoline.

Oil prices hit a record $119.93 a barrel on Monday after a weekend refinery strike closed a pipeline system that delivers a third of Britain's North Sea oil to refineries in the U.K.