The Main Committee will hold its next session on 21 April.
The proposal for the election convention came on Wednesday afternoon after party leader Ivica Racan earlier in the day tendered his resignation stating that he was faced with a serious illness and continued his fight for life.
Antunovic told a press conference that she had decided for the proposal after she had consulted the Main Committee's chairman, Tonino Picula, following the announced resignation by Racan.
Asked whether she would run for party president, Antunovic responded that "calculations with names (of candidates) are in bad taste and impossible, or to say the very least too early".
Another prominent SDP member, Zoran Milanovic, who is also believed to be a possible candidate for the party leader's post, agreed with Antunovic and added that there would be much more speculations in the coming days.
"The announcement of the candidacy does not depend on individuals but on the procedure and support of the party," Antunovic said at the press conference in the party's headquarters.