Members of nine opposition parties who met last night made some headway in their bid to avoid three-cornered fights.
But with more than one party still set on contesting one-third of the constituencies, the parties plan to meet again on Thursday evening.
National Solidarity Party (NSP) acting secretary-general Hazel Poa told reporters after the meeting at her party headquarters in Jalan Besar: "We have decided to keep the outcome of today's discussion confidential for the time being."
But, she added: "We reaffirmed our commitment to avoid three- cornered fights and that is what we are working towards on Thursday."
The Straits Times understands from sources that a key sticking point at the meeting was over Marine Parade Group Representation Constituency (GRC) and MacPherson Single Member Constituency (SMC), which was carved out from the GRC.
SITUATION AFTER TALKS
STRAIGHT FIGHT WITH THE PEOPLE'S ACTION PARTY
Bukit Panjang: Singapore Democratic Party (SDP)
Hougang: Workers' Party (WP)
Pioneer: National Solidarity Party (NSP)
Potong Pasir: Singapore People's Party (SPP)
Punggol East: WP
Radin Mas: Reform Party (RP)
Sengkang West: WP
East Coast: WP
Aljunied : WP
Nee Soon: WP
Ang Mo Kio: RP
Pasir Ris-Punggol: Singapore Democratic Alliance (SDA)
CLOSE TO RESOLUTION
Bukit Batok: SDP and NSP
Fengshan: WP and Democratic Progressive Party (DPP)
Hong Kah North: SPP and DPP Mountbatten: SPP and NSP
Holland-Bukit Timah : Singaporeans First (SingFirst) and SDP
Bishan-Toa Payoh: SPP and DPP
Tanjong Pagar: SingFirst and DPP
MacPherson: WP and NSP
Chua Chu Kang: NSP and People's Power Party (PPP)
Jalan Besar: WP and NSP
Marsiling-Yew Tee: NSP and SDP
West Coast: SingFirst and RP
Jurong: SingFirst and RP
Marine Parade: WP and NSP
Sembawang: SDP and NSP
Tampines: NSP and SingFirst
The NSP believes it should have first dibs in both areas because it stood in Marine Parade in the 2011 General Election.
The WP, meanwhile, is staking its claim because the redrawn boundaries of the GRC will absorb the Joo Chiat single-seat ward, which the WP lost by 388 votes in 2011.
Last night's meeting was the first to be called since redrawn electoral boundaries were made public on July 24. The meeting of all opposition parties has traditionally been held ahead of recent general elections, to discuss contesting as many seats as possible and to avoid three-cornered fights, which are seen as splitting the opposition vote and reducing their chances of winning against the People's Action Party (PAP).
Representatives from all nine parties set to contest the election turned up last night.
Members of the smaller Socialist Front and the Singapore National Front, which are not contesting the polls, also attended.
The Workers' Party (WP), which has seven elected MPs in Parliament, was represented by Aljunied GRC MP Muhamad Faisal Abdul Manap, Non-Constituency MP Yee Jenn Jong - who stood in Joo Chiat in 2011 - and executive committee member Daniel Goh.
WP chairman Sylvia Lim would have attended the meeting if not for her Meet-the-People session which was scheduled at the same time as the pow-wow, the party's representatives said.
Mr Faisal told reporters: "We want to avoid three-cornered fights."
WP chief Low Thia Khiang had said last week the party will contest East Coast GRC, Nee Soon GRC and Sengkang West SMC.
WP will also stand in Jalan Besar GRC, which includes most of the soon-to-be-defunct Moulmein-Kallang GRC, where it stood in 2011.
It will also contest single seats that have been carved out of East Coast and Marine Parade, respectively: Fengshan and MacPherson.
WP representatives last night told the meeting that the party remains firm in its decision to contest these seats.
The Straits Times understands that several of those present at the meeting last night were disappointed that the WP leaders, Mr Low and Ms Lim, did not turn up.
Those present who were not from the WP or NSP also took a vote on which of these two parties should contest Marine Parade GRC. The majority voted for the NSP to contest Marine Parade, sources at the meeting said on condition of anonymity.
But the vote is non-binding and merely reflects sentiments among those present ahead of Thursday's meeting.
The WP has initiated talks with the NSP over Marine Parade GRC and MacPherson SMC.
But both sides have continued to walk the ground in the two constituencies even though they say they are willing to compromise.
It is also unclear if the NSP wants to be seen to be yielding to the WP once again, having made way in the 2011 polls for the WP to stand in the soon-to-be-defunct Moulmein-Kallang GRC.
In the run-up to the huddle, party leaders had expressed confidence that they could iron out their differences in areas where there are overlapping interests.
Yesterday, the Democratic Progressive Party (DPP) led by Mr Benjamin Pwee gave way to the Singapore People's Party (SPP) led by Mrs Lina Chiam over Potong Pasir SMC, where Mrs Chiam lost by 114 votes in the 2011 election.
SPP veteran Chiam See Tong held the seat for 27 years, but left to lead a team in neighbouring Bishan-Toa Payoh GRC, where the party lost.
However, the DPP will likely work with SPP to field a joint team to contest Bishan-Toa Payoh GRC, said a source. DPP is also said to be in talks with the Singaporeans First (SingFirst) party to form a joint team in Tanjong Pagar GRC, which has never been contested since its formation in 1991.
SingFirst party chief Tan Jee Say told reporters before the meeting yesterday night: "Our journey to the west begins in Tanjong Pagar."
Parties have yet to reach agreement on who should contest five of the six four-MP GRCs. They include Chua Chu Kang, where the People's Power Party and NSP want to contest, as well as Holland-Bukit Timah, where the Singapore Democratic Party (SDP) and SingFirst want to contest.
SDP and NSP also want to contest the new Marsiling-Yew Tee GRC, while both SingFirst and the Reform Party (RP) are eyeing West Coast GRC.
Parties have also not agreed on who will contest four of the eight five-MP GRCs. Apart from Marine Parade, two parties want to contest Jurong, Sembawang and Tampines GRCs.
There was only one three-cornered fight in 2011 - in Punggol East, involving the PAP, WP and Singapore Democratic Alliance (SDA).
SDA chief Desmond Lim, who lost his deposit in that contest, will lead a team in Pasir Ris-Punggol GRC and said last night that his party will not contest against other opposition parties.
Multi-cornered fights have often seen weaker opposition candidates lose their election deposits as well.
Under election rules, candidates who secure less than 12.5 per cent of valid votes cast would lose their deposits.
The deposit per candidate is 8 per cent of the total allowances payable to an elected MP in the preceding year, rounded to the nearest $500. In the 2011 election, the deposit required was $16,000.
Going by last night's meeting, every one of the 89 seats is set to be contested at the next election.
If they are, come Nomination Day, it will be the first time since independence that every eligible voter gets a chance to cast their ballot at a general election.
• Additional reporting by Lim Yan Liang and Toh Yong Chuan