STOCKHOLM, Nov 22 (Reuters) - Sweden"s parliament will vote on Wednesday on approving Social Democrat leader Magdalena Andersson as the country"s first woman prime minister, the Riksdag speaker said on Monday, amid uncertainty over whether she can cobble together enough support. Andersson, currently finance minister, has been locked in negotiations with the Left Party to secure their backing to take over from Stefan Lofven, who handed in his resignation as prime minister earlier this month. read more "Unfortunately, we have not straightened out all the details, and we have not reached a deal," Andersson told reporters. "Therefore, it is not clear yet that I will be passed by the Riksdag, but the Speaker has decided to put me forward as a candidate in a prime ministerial vote." Andersson said negotiations with the Left Party, which wants a say in policy in return for its support, had been constructive. "I am still hopeful that we can reach a deal," she said. From 2014, Lofven led a fragile, minority coalition government with the Greens that relied on support from the Centre and Left Parties. Andersson replaced Lofven as leader of the Social Democrats earlier this month. The Centre Party has said it will not block Andersson. read more If Andersson does not get parliament"s backing to become prime minister, it is unclear who can lead the country. The head of the Moderates, the biggest opposition party, has said he does not see a way to form a centre-right government given the current political deadlock. That could force the speaker to call a snap election, just 10 months before the country is due to hold a scheduled vote. Without a deal with the Left it is also unclear whether the government can pass its budget, which lawmakers vote on later on Wednesday. Parliament will vote on whether to confirm Andersson as prime minister at 0800 GMT on Wednesday. Lofven is leading a caretaker government until a new prime minister is appointed. Reporting by Simon Johnson and Johan Ahlander; editing by Niklas Pollard and Alex Richardson