The leader of Spain's Catalonia region has announced that his pro-independence government will face a confidence vote in September after a party backing his coalition decided not to support the regional spending plan.

Carles Puigdemont made the declaration Wednesday after the radical left Popular Unity Candidacy party broke ranks with the "Together for Yes" block formed by pro-independence parties from the rest of political spectrum.

The leftist party known as CUP says the regional budget doesn't do enough to support social and pro-secession programs.

It was known as a colorful oddity in Catalan politics until it proved crucial last year for providing the support needed to create a pro-independence majority in Catalonia's 135-seat regional parliament.