But Andersson said she had told the speaker of parliament she hoped to be appointed prime minister again as the head of a single-party government, and the prospects of that happening appeared fairly strong given support from other parties.
The Green Party quit after parliament rejected the coalition's budget bill.
"I have asked the speaker to be relieved of my duties as prime minister," Andersson told a news conference. "I am ready to be prime minister in a single-party, Social Democrat government."
The Green Party said it would support her in any new confirmation vote in parliament, while the Centre Party promised to abstain, which in practice amounts to the same as backing her candidacy. The Left Party has also said it would back her.