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US Secretary of Energy Rick Perry, who has been drawn into the Trump impeachment inquiry, will resign.

President Donald Trump has confirmed the former Texas governor will depart his administration.

Mr Perry's exit had been rumoured for months even before he became entangled in a controversy over Ukraine.

US lawmakers are scrutinising Mr Perry's role in efforts to pressure Ukraine's president to investigate Mr Trump's political rival, Joe Biden.

At an event in Texas, Mr Trump said: "He's [Rick Perry] been outstanding and we already have his replacement, Rick has done a fantastic job at energy.

"But it was time, three years is a long time, and he'll be leaving towards the end of the year."

Mr Trump followed up on Friday by thanking Mr Perry for his "outstanding work" and naming his deputy, Dan Brouillette, as the new energy secretary.

Mr Perry was one of three US officials - dubbed the Three Amigos - who had influence over US policy on Ukraine.

On Wednesday, Mr Perry refused to say whether he would comply with a subpoena from Democratic impeachment investigators in Congress who are probing whether Mr Trump illegally sought to have Ukraine open an investigation into Democratic presidential candidate Joe Biden.

In a 2011 campaign for the presidency, during a live TV debate, Mr Perry forgot the name of a government department that he planned to abolish.

The name of the agency that had slipped his mind was the energy department.

But as Trump energy secretary, he presided over a significant expansion of the department's budget, while championing a surge in US fossil fuel output.

During the 2016 election season Mr Perry's hopes once again quickly fizzled.

He had called Mr Trump's candidacy "a cancer on conservatism", only to ultimately join his administration.