LONDON 

Former Prime Minister Alexander Stubb was sworn in on Friday as the 13th president of Finland, the Nordic country that joined the NATO military alliance last April. 

"We are now facing a new era," Stubb said as he formally took over from Sauli Niinisto as head of state in an inauguration ceremony in parliament in Helsinki.

"As a result of allying ourselves militarily and joining NATO we have taken the final step into the Western community of values, where the Republic of Finland has belonged to in spirit throughout its independence," he added.

The 55-year-old replaced Niinisto, who remained the head of state for two six-year terms. He was elected in a narrow Feb. 11 runoff victory against former Foreign Minister Pekka Haavisto.

"Finland’s foreign and security policy is founded on value-based realism," he said. "Its starting point is a strong alliance with the European Union and NATO. At the same time, it is based on the belief that the foundation of the new international system and peace lies in reforming and strengthening the UN."

Finland, which has a land border with Russia, joined as the 31st member of NATO last year in response to Moscow's war on Ukraine. It’s neighbor, Sweden, is also in the final stages of accession into the alliance.

Stubb said he will work with "vigour and determination" for an "open, safe and international Finland."

"I promise to defend democracy, the freedom of speech and the rule of law in all situations. I promise to listen, discuss and care. I promise to fight to ensure that Finland will remain a good country in the future as well – the best country in the world for us Finns," he said.

Ninisto, for his part, said "everything will keep on changing," requiring "flexible and rapid ability to adapt oneself."

But, he added, a lot will also remain unchanged. "The human mind, that is. Diplomacy is still also a solo sport that requires discretion. That way even small countries can get their voice heard," the former leader said.