British Prime Minister Liz Truss will call on like-minded nations to combat authoritarianism together, drawing on Russia's invasion of Ukraine to underline the need to push back against those "who weaponise the global economy".

Truss, at the U.N. General Assembly on her first international trip as Britain's new prime minister, has been a vocal supporter of Ukraine since Russia's invasion. She has pledged to match or exceed her country's 2022 spending on military aid next year.

She will address the United Nations on Wednesday, on the second full day of her trip to New York, which she is hoping to use to reset Britain's so-called special relationship with the United States after ties soured over Brexit.

In the U.N. speech, Truss will point to domestic reforms she hopes to oversee - measures, she says, will offer Britain the "strong economic foundations" needed to constrain authoritarianism by securing energy independence and safeguarding supply chains.

"The free world needs this economic strength and resilience to push back against authoritarian aggression and win this new era of strategic competition," she will say, according to excerpts from her speech.

"We will no longer be strategically dependent on those who seek to weaponise the global economy."

She will say the Group of Seven economic powers and other like-minded partners must act as an "economic NATO," collectively defending prosperity and coming to the aid of any partner targeted by an aggressive government.

But countries must also invest more in physical security. She will repeat a commitment to increase defence spending to 3% of Britain's gross domestic product by 2030.

The New York visit is the first event in a few days of frenzied government activity, when her ministers are expected to set out a new energy support package for businesses, a plan to help the National Health Service and much-promised tax cuts.

Britain's King Charles meets with Prime Minster Liz Truss
Britain's King Charles meets with Prime Minster Liz Truss