The U.S. military has put countering China and Russia at the centre of a new national defence strategy unveiled on Friday, the latest sign of shifting American priorities after more than a decade and a half of focusing on the fight against Islamist militants.

In unveiling the new strategy, which will set priorities for the Pentagon for years to come, Defence Secretary James Mattis called China and Russia "revisionist powers" that "seek to create a world consistent with their authoritarian models."

The so-called National Defense Strategy represents the latest sign of hardening resolve by President Donald Trump's administration to address challenges from Russia and China, at the same time he is pushing for improved ties with Moscow and Beijing to rein in a nuclear North Korea.

"We will continue to prosecute the campaign against terrorists that we are engaged in today, but great power competition, not terrorism, is now the primary focus of U.S. national security," Mattis said in a speech in Washington, D.C., presenting the strategy document, the first of its kind since at least 2014.

It sets priorities for the U.S. Defense Department that are expected to be reflected in future defence spending requests. The Pentagon on Friday released an unclassified 11-page version of the document, which does not provide details on how the shift towards countering China and Russia would be carried out.

Russian Foreign Minister Sergei Lavrov, speaking through an interpreter at a news conference at the United Nations, said the U.S. was using a confrontational approach.

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Russian Foreign Minister Sergei Lavrov speaks during a security council meeting at the United Nations in New York on Friday. He says the U.S. defence strategy uses a confrontational approach. (Shannon Stapleton/Reuters)

"It is regrettable that instead of having a normal dialogue, instead of using the basis of international law, the U.S. is striving to prove their leadership through such confrontational strategies and concepts," Lavrov said.

"We're open for dialogue. We're prepared to discuss military doctrines," he added.

There was no immediate response from China.

Elbridge Colby, deputy assistant secretary of defence for strategy and force development, said at a briefing with reporters that Russia was far more brazen than China in its use of military power.

Russia annexed Ukraine's Crimean peninsula in 2014 and intervened militarily in Syria to support its ally, Syrian President Bashar al-Assad. Still, Moscow was limited by its economic resources, Colby said.

China, on the other hand, was described as economically and militarily ascendant. China has embarked on far-reaching military modernization that Colby said was in "deep contravention to our interests."

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U.S. President Donald Trump, flanked by Secretary of State Rex Tillerson, left, and Defence Secretary James Mattis, holds a cabinet meeting at the White House in Washington, D.C., on Jan. 10. (Jonathan Ernst/Reuters)

Support for alliances

The document also lists North Korea among the Pentagon's priorities, citing the need to focus U.S. missile defences against the threat from Pyongyang, which beyond its nuclear weapons has also amassed an arsenal of biological, chemical, and conventional arms, the document says.

International alliances would be critical for the U.S. military, by far the world's best-resourced, the document says. But it also stresses a need for burden-sharing, an apparent nod to Trump's public criticism of allies who he says unfairly take advantage of U.S. security guarantees.

Trump has called the NATO alliance "obsolete," but Mattis said the U.S. would strengthen its traditional alliances while building new partnerships and listening more to other nations' ideas.

"We will be willing to be persuaded by them, recognizing that not all good ideas come from the country with the most aircraft carriers," Mattis said.

The Pentagon is also working on a policy document on the country's nuclear arsenal. While Mattis did not specifically address that review, he said the priority is deterrence.

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Mattis talks to U.S. Marine Corps troops at a rifle range at Guantanamo Bay, Cuba, on Dec. 21. 2017. (Robert Burns/Associated Press)

"How do we maintain a safe and effective nuclear deterrence so those weapons are never used? It is a nuclear deterrent. It is not a war fighting capability unless it is the worst day in our nation or the world's history," Mattis said.

Mattis had harsh words for the U.S. Congress and its inability to reach agreement on budgets.

The U.S. military's competitive edge has eroded "in every domain of warfare" he said, partly because of inconsistent funding. 

"As hard as the last 16 years of war have been, no enemy in the field has done more to harm the readiness of the U.S. military than the combined impact" of spending caps and short-term funding.

In sheer spending terms, the United States' military outlay per year is still far more than China and Russia. U.S. military expenditure totalled $611 billion US in 2016, while China spent $215 billion and Russia's military expenditure was $69.2 billion, according to the Stockholm International Peace Research Institute.

With files from CBC News