All other NATO members had already backed Dutch Prime Minister Mark Rutte to become the next chief of the alliance.
All other NATO members had already backed Rutte, a staunch ally of Ukraine and outspoken critic of Russian President Vladimir Putin, to take over from Jens Stoltenberg, who is stepping down this year after a decade in charge.
This week, Hungary lifted its veto on Rutte’s candidacy after the long-serving Dutch prime minister gave written guarantees that he would not force Budapest to take part in the military alliance’s new plans to provide support to Ukraine should he be appointed.
NATO makes all of its decisions by consensus, giving any of its 32 member countries an effective veto, including on whether they should take part in any joint effort or operation.
Turkey had also voiced opposition to Rutte’s bid but lifted its objections in April.
With the war in Ukraine on NATO’s doorstep and European nations concerned about the possible return of NATO-critical Donald Trump to the White House after the November presidential election in the United States, alliance members concluded the highly experienced Rutte was the best person for the post.
As it announced Iohannis’s decision on Thursday, Romania’s Supreme Council of National Defence said it would donate one of the country’s two operational Patriot missile systems to Ukraine, responding to pleas from Kyiv to its allies for more air defence assistance.
Ukrainian President Volodymyr Zelenskyy said Romania’s decision “will bolster our air shield and help us better protect our people and critical infrastructure from Russian air terror”.
The supreme council, which is chaired by Iohannis, said the president had informed NATO last week of his decision to withdraw and Romania would now support Rutte’s candidacy.
With all 32 NATO members now backing the Dutchman, diplomats said they expected the alliance’s governing North Atlantic Council to formally select him for the post in the coming days.
Rutte will face the challenge of maintaining support for Ukraine’s fight against Russia’s invasion while guarding against any escalation that could draw NATO directly into a war with Moscow.
Under Rutte, the Netherlands has in recent years ramped up defence spending above NATO’s target of 2 percent of its gross domestic product (GDP). It is providing F-16 fighter jets, artillery, drones and ammunition to Kyiv as well as investing heavily in its own military.
Former Norwegian Prime Minister Stoltenberg’s term at the helm of NATO will end on October 1. He took office in 2014, just a few months after Russia annexed Ukraine’s Crimean Peninsula.
Stoltenberg oversaw NATO’s shift from an alliance mainly engaged in crisis management missions in places such as Afghanistan back to its roots of defence against Russia.
Four countries have joined NATO since Stoltenberg took office: Montenegro, North Macedonia, Finland and Sweden.
By giving the top job to Rutte, the alliance would pass up the opportunity to appoint its first female secretary-general – something multiple member states had said they were eager to do.
Estonian Prime Minister Kaja Kallas was widely considered a contender for the role with strong support from Eastern European countries. But she was seen as too hawkish towards Russia by some Western member states.
Kallas is now the leading candidate to be the next European Union foreign policy chief, according to diplomats.
Iohannis, whose second term as Romanian president ends this year, has repeatedly said Eastern European states need better representation in Euro-Atlantic leadership roles.
Romania, a member of both NATO and the EU, has raised defence spending to 2.5 percent of its GDP in response to Russia’s 2022 invasion of Ukraine.