US President Donald Trump praised Nigerian President Bola Tinubu for his actions against violence, according to a letter released by Nigeria's presidency on Wednesday, in contrast to the US leader's threats late last year over treatment of that country's Christians.

Trump said he appreciated Tinubu's "decisive leadership on behalf of the Nigerian people" and applauded his efforts to address "the violence affecting Christian communities," according to the letter, which was dated July 6.

"It is a true honour to stand with you in the fight against terrorists and to make the Federal Republic of Nigeria stronger and more prosperous," Trump wrote.

The letter signals a warming of ties between Abuja and Washington since Trump last November accused the government of failing to protect Christians from extremist violence and threatened to cut aid to Nigeria and take possible military action.

Nigeria rejected the allegations, saying insecurity affected citizens of all faiths.

According to the Nigerian presidency, the two countries established a joint security working group last year to expand intelligence sharing, training, and operations against militant groups.

The letter was released days after US Assistant Secretary of State for Africa Frank Garcia visited Abuja for talks on strengthening security cooperation.