Goodluck Jonathan, new acting president of Nig­eria, received another boost to his authority on Friday when the US backed his elevation after months of uncertainty in Africa’s biggest energy producer.

Parliament’s decision on Tuesday to confer full powers on Mr Jonathan, the vice-president, appeared to exceed its constitutional authority. But the move has lifted the uncertainty caused by the 11-week absence in a Saudi Arabian hospital of Umaru Yar’Adua, the stricken ­president.

“The best interests of the country and the future of Nigeria have been well served by this action,” said Robin Sanders, the US ambassador. “We believe that the principle of democracy [has] been served well in Nigeria.”

These warm comments were a marked contrast to recent frosty relations between the US and its fifth biggest oil supplier.

Even before Umar Farouk Abdulmutallab, a young Nigerian, allegedly attempted to destroy a US airliner on Christmas day, Washington had sharpened its rhetoric towards a country plagued by misrule.

While visiting Nigeria last August, Hillary Clinton, the US secretary of state, blamed a “lack of transparency and accountability” for eroding the “legitimacy of the government”.

The African Union and the UK have hailed the promotion of Mr Jonathan, who has moved swiftly to consolidate his authority.

He has pledged to use the remaining year of the presidential term to address a chronic power shortage, end unrest in the Niger delta, where most of the country’s oil reserves are found, and reform the electoral system.

Foreign investors have been troubled by the legal contortions that allowed Mr Jonathan to take control. But they, like the main foreign powers, have welcomed the end of an unsettling political vacuum.

“It’s obvious that all these countries have been dealing with nobody,” said Atedo Peterside, a member of the national economic management team. “Now they feel that the country has a leader.”

Nigeria’s resources have become the focus of international competition. Gaz­prom, the Russian gas monopoly, stole a march on European companies last year when it announced a $2.5bn (€1.8bn, £1.6bn) investment in Nigerian gas.

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