Atiku Abubakar said the call was an “acknowledgement of a fraudulent election”.

Mr Blinken on Tuesday said he had spoken to Mr Tinubu to “emphasize his continued commitment to further strengthen the US-Nigeria relationship with the incoming administration”.

He noted that the relations built on shared interests and people ties “should continue to strengthen under President-elect Tinubu’s tenure”.

But Mr Abubakar, who is a former Nigerian vice-president, said he was “in disbelief” over the call, which he said was a contradiction of US’s publicly stated position on the election.

He said it was “inconceivable” that the US, which was well briefed on the “sham election” was giving legitimacy to it.

Petitions contesting the victory of Mr Tinubu were filed in March by several presidential candidates Mr Abubakar and Peter Obi, who was placed third in the 25 February polls.

The appeals court tribunal must decide on the petitions within 180 days from the date of filing. The cases may end up in the Supreme Court for a conclusive verdict.

Mr Tinubu is due for inauguration on 29 May.