Gillard calls for Australian Labor Party leadership vote February 23, 2012 -- Updated 0042 GMT (0842 HKT) NEW: Tensions between the two have increased in recent days NEW: Julia Gillard replaced Kevin Rudd as prime minister in June 2010 Gillard's role as leader of the Labor Party is challenged by Rudd Leadership ballot on Monday "will settle this question once and for all," Gillard says (CNN) -- Australian Prime Minister Julia Gillard will put her future in the hands of her Labor Party parliamentary colleagues next Monday, she told reporters Thursday in Adelaide. Her announcement ends months of speculation about a challenge to her leadership by Kevin Rudd, whom she replaced as prime minister in 2010. She said the leadership ballot in Canberra on Monday "will settle this question once and for all." On Wednesday, while visiting Washington, Rudd resigned as Gillard's foreign minister, saying before he departed to return to Australia, "I do not believe that Prime Minister Gillard can lead the Australian Labor Party to success in the next election." But Gillard was unbowed. "I expect to win," she said. Australia's next election has to be held by the end of November 2013. Observers had predicted a showdown could take place next week when Parliament resumes. But Rudd's announcement in Washington in the middle of the night caught people by surprise. In a statement Wednesday, Gillard called Rudd "a strong and effective advocate for Australia's interests overseas" and said he "strongly pursued Australia's interests in the world." "I am disappointed that the concerns Mr. Rudd has publicly expressed this evening were never personally raised with me, nor did he contact me to discuss his resignation prior to his decision," she said. Gillard took over in 2010, but she has struggled to achieve high approval ratings.