* PM faces party leadership challenge this month
* Defeat could trigger election, international bailout
* PM warns "time for games is over" (Adds quotes, background)
By Marja Novak
LJUBLJANA, Oct 3 (Reuters) - Slovenian Prime Minister Alenka Bratusek threatened on Thursday to quit the government if she loses a party leadership vote later this month, saying the country had no time for "games" as it seeks to avert an international bailout.
Bratusek's resignation would almost certainly trigger a snap election, delaying a raft of crisis measures to shore up Slovenia's finances and prevent the country from becoming the latest member of the 17-nation euro zone to seek EU/IMF aid.
In a direct challenge to Bratusek's authority, Ljubljana mayor Zoran Jankovic, who created the Positive Slovenia party in 2011 but resigned in February, announced on Wednesday he would challenge her for the party leadership at a congress on Oct. 19.
Bratusek's coalition allies have said they would quit the governing alliance if Jankovic, who has been tainted by accusations of corruption, returns as party leader. The government already faces a confidence vote, expected in November, over the 2014 national budget..
Analysts say it is far from certain which way the party leadership vote will go. Technically Bratusek can continue as prime minister even if not leader of the party, but she made clear she would not.
"The fact is that someone else will have to try to form a government if I would not have sufficient support in the party," Bratusek said in a statement.
"My biggest worry is how to effectively overhaul the banks, confirm a sustainable budget, start a new development and investment cycle," she said, warning: "It should be clear to everyone that the time for games is over." ($1 = 0.7358 euros) (Writing by Matt Robinson)