While the primary ability to act lies with the Indonesians, the Singapore Attorney-General is investigating what can be done against firms involved in causing the haze, Foreign Minister K. Shanmugam said on Saturday.
"We will offer no succour or refuge if the actions of the companies have been deemed illegal in Indonesia and impacted on Singapore," he said during a briefing to reporters.
The stern warning came a day after the Indonesian government named some firms in Riau province involved in the blazes, and which have Singapore links.
The minister pointed out that "serious" issues of jurisdiction and international law need to be considered, so he has asked the Attorney- General to look into what can be done to such companies if there is proof that they contributed to the haze.
Mr Shanmugam, who also holds the Law portfolio, said he expects to know what Singapore "can or cannot do by this weekend".
But the primary ability to act lies with the Indonesians as the firms are located there, he stressed.
"We would like to see strong, firm, effective action taken against them in Indonesia, because that's where they are, that's where the actions are taking place, that's where their offices are, the senior people.
"We'd really like to see firm, quick action and any assistance we can render in that respect, we will do so."
Singapore also needs to depend on Indonesia to provide evidence on who is involved, the minister said.
"Indonesian investigation authorities need to be on the ground, I cannot send my police officers in there to investigate," he said.
"That will be a breach of Indonesian sovereignty and Indonesia will not agree to that."
On its part, Singapore has offered assistance on several levels to combat the fires, he revealed.
These range from aircraft to technical assistance and offers of manpower.
Mr Shanmugam said: "It has yet to be taken up. And (in) 2005, we offered assistance of our aircraft and that was accepted, but this time that offer has not yet been accepted."
In 1997, Singapore also helped in Indonesia's firefighting efforts by providing computers, global positioning systems and a Singapore Armed Forces C-130 aircraft and crew.
Acknowledging that the haze has been a longstanding issue, Mr Shanmugam told reporters that it did not just have an environmental impact on Indonesia or the region, but also a global one.
"In 1997... studies suggest that the carbon dioxide emission from peat fires has contributed to a substantial part of global carbon dioxide emissions in that year. Therefore we have urged Indonesia to take decisive action.
"This is not slash and burn, this is not an act of nature by itself, these are actions by companies for commercial profit."
He also referred to Indonesian Foreign Minister Marty Natalegawa's remark last Friday that they would not apologise to Singapore for the haze.
Mr Shanmugam said: "I'm not sure that we're asking for an apology. What we want is for the problem to be solved, that is really the point."