Republican presidential nominee Donald Trump said he'd end U.S. oil imports from OPEC and approve Keystone XL, though critics said he knows little about energy.

Trump was the keynote speaker Thursday at a petroleum conference in North Dakota, the No. 2 oil producer in the United States. The economy for North Dakota is under pressure from declines in the crude oil market, with production from the Bakken shale basin down almost 10 percent from its peak in December 2014.

Trump in his prepared remarks said his presidency would remove obstacles standing in the way of further exploration. The state rig count for Friday of 29 is 65 percent lower than this date last year, though slightly above the number reported earlier this week.

"Any market has ups and downs, but lifting draconian barriers will ensure that we are no longer at the mercy of global markets," the nominee said.

The head of a North Dakota oil and gas commission has been critical of policies enacted by the Bureau of Land Management and the Environmental Protection Agency, an agency Trump said he'd dismantle if elected.

A surplus in crude oil, brought on in part by higher U.S. production, sent oil prices tumbling below the $100 per barrel mark in 2014. A rally in 2016 was supported by proposals from some members of the Organization of Petroleum Exporting Countries to hold production static, though that move unraveled because Iran said it wanted to regain a market share lost to sanctions.

In his remarks, Trump said the United States would become "totally independent" from OPEC, while at the same time working with allies in the Middle East to develop a "positive energy relationship as part of our anti-terrorism strategy."

Seven of the top 10 oil exporters to the United States are members of OPEC, accounting for more than 45 percent of the total. Canada is the No. 1 oil exporter to the United States and Trump said that, if elected, he'd sign the permits needed to build the cross-border Keystone XL oil pipeline, which Washington rejected largely on environmental grounds.

Trump clinched the nomination during his trip to North Dakota, though few official statements emerged in support of his policies after his speech in Bismark. When pressed for a comment, the American Petroelum Institute pointed to the broad energy platform it's advocating for whoever takes office, saying only that energy is its primary candidate.

Michael Brune, the executive director of the Sierra Club, said Trump's speech highlighted a basic lack of understanding about energy policy.

"There are open pools of oil and drilling wastewater in North Dakota right now that are deeper than Trump's understanding of energy issues," he said in a statement.