WASHINGTON (REUTERS, WASHINGTON POST) - US Deputy Attorney General Rod Rosenstein, who appointed Special Counsel Robert Mueller in May 2017 to investigate links between the Russian government and President Donald Trump's campaign, said on Monday (April 29) he was resigning from his post.

In a letter to Mr Trump, Mr Rosenstein echoed two of Mr Trump's signature phrases, writing that he helped staff the department with officials "devoted to the values that make America great" and adding that "we always put America first".

Mr Rosenstein's departure had been expected since the beginning of the year, but the date was repeatedly pushed back as special counsel Mueller wound down his investigation and compiled a report detailing his findings.

Since his first days on the job, Mr Rosenstein's role in the Trump administration has been controversial, from the firing of then-FBI Director James Comey in May 2017 to the conclusion reached by Rosenstein and Attorney General William Barr that the president had not committed obstruction of justice.

In his resignation letter to Mr Trump, Mr Rosenstein praised the president for his personal charm and policy goals.

"As I submit my resignation effective on May 11, I am grateful to you for the opportunity to serve; for the courtesy and humour you often display in our personal conversations; and for the goals you set in your inaugural address: patriotism, unity, safety, education, and prosperity, because 'a nation exists to serve its citizens'," Mr Rosenstein wrote.