The U.S. is overtaking Russia as the world's largest producer of oil and gas because of increased tapping of shale gas within the U.S.

Russia is struggling to maintain its output of oil but has yet to tap its unconventional gas reserves by adopting new technologies such as hydraulic fracturing.

The U.S. produced the equivalent of about 22 million barrels a day of oil, natural gas and related fuels in July, according to figures from the U.S. Energy Information Administration and the International Energy Agency.

Moscow's forecast for 2013 oil-and-gas production works out to about 21.8 million barrels a day.

The change is reshaping oil markets and could redefine which countries are considered petroleum-rich over the next 20 years.

Canada still sells most of its oil to the U.S. market, about 2.4 million barrels of crude oil per day. But demand from the U.S. for both oil and gas is flattening, despite a return to rising consumption of petroleum products as the U.S. economy rebounds.

U.S. natural gas imports down 32%

Canada remains the biggest supplier of oil and gas to the U.S., but the Canadian Association of Petroleum Producers recommends developing other markets, because of the vast untapped reserves in the U.S.

U.S. imports of natural gas have fallen 32 per cent and crude oil imports fell 15 per cent in the last five years.

Russia produced an average 10.8 million barrels a day of crude oil in the first half of the year while the U.S. produced about 9.9 million barrels.

But U.S. natural gas production has overtaken Russian production for the first time since 1982, at 66 billion cubic feet a day. The U.S. has moved heavily into fracking to remove natural gas from shale formations.

Russia is said to have large reserves of shale gas and might increase its output in coming years.