COPENHAGEN, Denmark (AP) — Sweden's Foreign Minister Tobias Billström, who steered the Scandinavian country along a sometimes bumpy road to NATO membership and stood tall on supporting Ukraine, stunned the political establishment Wednesday by saying he was leaving the Swedish government next week.

“It has not been an easy decision but something that I have thought about and processed for some time,” Billström wrote on X.

Billström became foreign minister in October 2022, when Prime Minister Ulf Kristersson formed a coalition government with his own conservative Moderate Party, the smaller Christian Democrats and the Liberals.

In May 2022, Sweden and neighboring Finland sought NATO membership, ending decades of post-World War II neutrality and centuries of broader non-alignment with major powers as security concerns in Europe spiked following Russia’s 2022 full-scale invasion of Ukraine.

After 18 months of delays, Sweden’s membership bid cleared the final hurdle in February Hungary gave its consent.

Turkey also objected to Sweden joining the alliance, but on Jan. 23, Turkish legislators voted in favor. Turkish President Recep Tayyip Erdogan put forth a series of conditions including a tougher stance from Stockholm toward groups that Turkey regards as threats to its security, such as Kurdish militants and members of a network it blames for a failed coup in 2016.

Sweden became the 32nd member of the military alliance in March. The 50-year-old Billström said on X that he had taken Sweden through “a sometimes challenging NATO process.”

On Facebook, Kristersson said that Billström had discharged his duties with “flying colors.”

Billström said on X that he would “leave politics completely. This means that I am also leaving my seat in the Riksdag,” the Swedish parliament. The 349-member assembly will convene next week after the summer recess.

Billström has not announced what he’ll do next and his replacement has not yet been named.