WATCH LIVE: Donald Trump to lay out 'America First' national security strategy in speech

President Donald Trump is set to lay out Monday a new National Security Strategy built upon his trademark "America First" slogan, which is expected to have economic security at its core.

WATCH LIVE VIDEO, EXPECTED TO BEGIN AT 2:00 PM ET, BELOW:

The US leader, who has dismantled the legacy of Barack Obama on issues ranging from climate change to free trade, and isolated Washington on the world stage, will unveil what is being billed as a comprehensive vision for tackling America's complex security challenges.

The new document, released periodically by the presidency, "affirms the belief that America's economic security is national security," an administration official said.

It also reflects a determination to push for balance in US economic relations with the rest of the world, especially China.

"The greatest weapon we have is our strong GDP," the official said, citing Defense Secretary Jim Mattis.

Trump has taken an aggressive stance on trade. He vows to reduce bilateral trade deficits, particularly with China, and has said he wants to level the playing field for American companies.

Asked on Monday about the expected US strategy, Beijing's foreign ministry Hua Chunying said US-China economic and trade relations "are mutually beneficial."

She added that she hoped the new US policy will contribute to "our common safeguard of the international peace and security."

Trump's National Security Strategy was a year in the making.

Beyond its focus on economic competitiveness, it will mark a break with his Democratic and Republican predecessors when it comes to "homeland" and border security, the US official added.

Trump has cracked down on immigration and wants a wall built on the Mexican border.

The new national security document is to be released following a speech by the president.

It identifies four main priorities: protecting the country and the American people, promoting American prosperity, preserving peace through strength and advancing American influence.

- Climate not a priority -

Addressing the United Nations in late September -- with a virulence rarely seen in that forum -- Trump hammered home his attachment to American "sovereignty" while calling into question many aspects of the multilateral world order.

But despite the fiery delivery, the address fell short of spelling out a veritable "Trump doctrine" regarding America's place in the world.

Asked about the role of climate change in the new document, the administration official said it "is not identified as a national security threat" to the US.

Ascending to power on a message resolutely skeptical of climate change, Trump said in June that he would pull the US out of the Paris agreement on climate change signed by almost 200 countries.

Obama was one of the main architects of the Paris pact to curb global warming, and had underscored on several occasions how climate and security had become intertwined.

A year before he left office, Obama said climate change would affect the way America's military must defend the country, through profound adjustments in organization, training and protection of infrastructure.

"Climate change is an urgent and growing threat to our national security, contributing to increased natural disasters, refugee flows and conflicts over basic resources like food and water," according to the last National Security Strategy, issued in February 2015 during Obama's tenure.

On that occasion he argued at length against the temptation to make hasty decisions in the management of international crises.

"In a complex world, many of the security problems we face do not lend themselves to quick and easy fixes," Obama wrote, calling for "strategic patience and persistence."