Alaskan oil production declined for the week ending June 19, though Lower 48 gains meant overall output increased, federal data show.

Alaskan oil production for the week ending June 19 dropped 12 percent from the previous week to 417,000 barrels per day. The four-week average of 478,000 bpd is about 8 percent lower year-on-year, the federal Energy Information Administration said in a status report.

Though Alaska is the No. 4 oil producer in the nation, its production is in decline as many state reserve areas reach maturation.

Production from the Lower 48 states increased only modestly in terms of percent, but the volumetric increase of 76,000 bpd to 9.18 million bpd led to an overall U.S. increase for the week ending June 19, data show. Total U.S. oil production for the week was 9.6 million bpd.

The slight increase comes as energy companies struggle with spending on exploration and production because of lower crude oil prices. Oil field services company Baker Hughes said there were two fewer rigs overall operating in the United State for the week ending June 19 than during the previous week.

Rig data paints a mixed picture, however. Texas, the No. 1 oil producer, recorded no change in weekly rig counts, while North Dakota, the No. 2 producer, gained a rig for the week ending June 19, Baker Hughes data show. North Dakota's oil production, however, has shown a steady decline since December.

The full-year 2016 production average is expected to be 9.3 million bpd, EIA said.

The United States imported less oil from its top two suppliers, Canada and Saudi Arabia, respectively, for the week ending June 19, federal data show. Among major exporters to the U.S. market, only Kuwait and Ecuador showed significant increases.