Prime Minister Jacinda Ardern of New Zealand said on Thursday that she would not seek re-election in the country’s election later this year. She said she would step down on Feb. 7.

In a tearful announcement in the New Zealand city of Napier, where Ms. Ardern’s Labour Party was hosting its summer caucus retreat, she said she did not feel emotionally equipped to complete another term.

“I believe that leading a country is the most privileged job anyone could ever have, but also one of the more challenging,” Ms. Ardern said. “You cannot and should not do it unless you have a full tank plus a bit in reserve for those unexpected challenges.”

She added: “This has been the most fulfilling five and a half years of my life. I am leaving because with such a privileged job comes a big responsibility.”

Labour lawmakers will elect a new leader of the party — and the country — in three days’ time, Ms. Ardern said.

Ms. Ardern said she had informed party members of her decision earlier in the day. She said would remain a member of Parliament for her electorate in the city of Auckland until April, in order to avoid the need for a by-election.

This is a developing story and will be updated.