LUSAKA (Reuters) - Zambia’s Foreign Affairs Minister Harry Kalaba has resigned, he said on his Facebook page, as a struggle in the ruling Patriotic Front (PF) over President Edgar Lungu’s ambitions to run for another term in office intensifies.

Kalaba is seen as a potential PF candidate in a 2021 presidential election but analysts say his chances of winning the PF nomination may stall if Lungu wins a court battle allowing him to run for a third term.

“We cannot proceed to manage national affairs with cold indifference when the levels of corruption are swelling and being perpetrated by those who are expected to be the solution,” Kalaba said in a Facebook post late on Tuesday.

Presidential spokesman Amos Chanda told Reuters State House had not received Kalaba’s resignation letter.

Experts said Kalaba’s resignation was intended to apply pressure on Lungu who is accused by his opponents of chasing an unconstitutional third term.

“People have started realizing that they will not get nominated as long as Lungu insists on standing,” Lee Habasonda, an analyst from the University of Zambia, told Reuters.

Zambia’s constitution limits presidents to two terms but Lungu argues that his first period as leader doesn’t count because he did not serve a full term after he assumed power following the death of predecessor Michael Sata in 2014.

Lungu was then elected for a five-year term in 2016.

Lungu in November warned constitutional court judges not to stop him running again and his allies have asked the Supreme Court to confirm that he will be eligible to stand.