By Fatos Bytyci

PRISTINA (Reuters) - Kosovo's constitutional court suspended the appointment of the speaker of parliament on Wednesday, deepening a political crisis over who gets to rule the impoverished Balkan country for the next four years.

Kosovo is locked in a battle between political parties over who should form the next government following an election six weeks ago.

Prime Minister Hashim Thaci's Democratic Party of Kosovo (PDK) emerged as the biggest party with 30 percent of votes, but opposition parties have joined forces in search of a majority in the 120-seat parliament to deny him a third term.

Suggesting it had the makings of a working majority, the opposition bloc last week elected Isa Mustafa, leader of the opposition Democratic League of Kosovo (LDK), as speaker of parliament, a first step towards forming a government.

But the vote happened only after the PDK declared the session adjourned and left the chamber. The party appealed to the constitutional court, which issued a statement on Wednesday saying it had suspended Mustafa's election pending a final ruling by Sept. 18.

"Parliament should refrain from any decision until the final ruling of the court," it said.

Thaci's PDK says it should form the government as winner of the election, but the opposition parties say only they have the necessary votes in parliament.