US President Joe Biden has appointed Pakistani-American lawyer Khizr Khan — also a critic of ex-president Donald Trump and the father of a soldier slain in Baghdad — as the commissioner for the US Commission on International Religious Freedom, according to a statement released from the White House.

The announcement is one of four such appointments and nominations, with the White House website saying that it "underscores the President’s commitment to build an Administration that looks like America and reflects people of all faiths".

Apart from Khan, Sharon Kleinbaum was appointed the commissioner of the United States Commission on International Religious Freedom, whereas Deborah Lipstadt was nominated for the post of special envoy to monitor and combat anti-semitism and Rashad Hussain as ambassador-at-large for international religious freedom.

The Office of International Religious Freedom said it "welcomed" the appointment. "We look forward to collaborating with them to advance religious freedom for all," it tweeted.

Khan, 71, is a Pakistan-born lawyer who criticised Trump for his disparaging remarks against American Muslims during the 2016 Democratic National Convention (DNC).

Khan’s son, Humayun Khan, was a US Army captain killed in 2004 while serving in Iraq. He is buried at Arlington cemetery, Virginia and was posthumously awarded top military medals — Bronze Star and Purple Heart.

Khan gave a passionate speech at the 2016 convention, along with his wife, Ghazala, in which he questioned whether Trump, then the Republican presidential nominee, had ever read the US Constitution. He pulled his own copy out of his pocket for emphasis — and said Trump had “sacrificed nothing and no one”.

After that, Trump frequently lashed out at the Khans, which they shrugged off as “proof of his ignorance and arrogance”. At one point Trump suggested that Ghazala did not speak during the DNC because of her Muslim faith.

After his speech, Khan was featured in campaign ads for Hillary Clinton, the Democratic Party’s presidential nominee, and his family’s story became a regular feature in her campaign speeches.

Khan, who was born in Gujranwala, works as a lawyer and also founded the Constitution Literacy and National Unity Project.

He immigrated to the US in 1980 and studied at Harvard Law School where he obtained his LLM (Master of Law) degree, according to the statement.

"He is licensed to practice law before the Supreme Court of the United States, various federal district courts, and Washington, DC and New York State courts.

"In his law practice, he devotes a substantial amount of his time to providing legal services to veterans, men and women serving in uniform, and their families," the statement reads.

Khan is the sixth Pakistani-American to join the Biden team since he entered the White House as the 46th US president on Jan 20. Biden, last month, inducted Lina Khan into his team as a top federal regulator to head the Federal Trade Commission.

He also previously nominated another Pakistani-American, Dilawar Syed, to serve as the deputy administrator of the Small Business Administration in March.

Before that, Biden had inducted Pakistani-American Salman Ahmed into his foreign policy team to serve as director policy planning at the US State Department. This was the second such induction of a Pakistani American in Biden's team.

The US president also chose a Pakistani-born climate expert, Ali Zaidi, to serve as his Deputy National Climate Adviser in December. The appointment had made Zaidi the highest ranking Pakistani-Ameri­can in the Biden administration.