The US hopes the two sides will continue to talk
Norwegian Foreign Minister Jan Petersen has met Sri Lanka's government and opposition, as part of efforts to revive the stalled peace process with Tamil Tiger rebels.
The discussions, in the capital, Colombo, came as a deadline for the rebels to say whether they will attend crucial donor talks next month in Japan expired.
The United States says it is in the rebels' best interests to go to Tokyo.
But there is no sign from the Tigers that they are ready to re-enter negotiations.
It is in the best interest of the peace process, the Tamil people and the Tigers themselves that the LTTE be at the table in Tokyo
Rebel officials pulled out of the proposed discussions and suspended peace talks last month, saying they were being marginalised.
Last week, Japan, a major aid donor to Sri Lanka, gave the Tigers until Wednesday to decide whether they would take part in the Tokyo talks.
The BBC's Frances Harrison in Colombo says the conference is crucial as it is expected Sri Lanka will attract up to $3bn of aid if the Tigers show they can work with the government they fought for so many years.
South 'not happy'
Mr Petersen is expected to meet the leader of the Liberation Tigers of Tamil Eelam (LTTE), Velupillai Prabhakaran, on Thursday.
We don't want them [the Tigers] to make demands that rouse the southern masses
Opposition leader Mahinda Rajapaksa
On Wednesday, the Norwegian foreign minister held talks with Sri Lankan Prime Minister Ranil Wickramasinghe, and opposition leader Mahinda Rajapaksa.
Mr Rajapaksa told the BBC Sinhala Service that people in the south were not happy about apparent concessions to the rebels.
"We don't want them to make demands that rouse the southern masses," he said.
There was no official word from the rebels, but a pro-Tamil website, Tamilnet.com, reported they were sticking to their demands, despite the deadline.
"The LTTE is of the view that before it participates in the Tokyo aid conference... the administrative, financial and other structures with adequate powers need to be established in order to
reconstruct the north-east and to rehabilitate and restore normal civilian life in the north-east," the website quoted moderate Tamil politicians as saying after talks with the rebels' political wing.
Earlier, US Assistant Secretary of State Christina Rocca told journalists in Colombo that it would help the peace process as a whole if the Tigers went to Japan.
US envoy Christina Rocca is listening to many local concerns
Ms Rocca defended her government's decision not to invite the Tigers to Washington, saying they would remain on the US terrorist list until they renounced violence and honoured democracy and human rights.
And she renewed a call by the US for Sri Lanka's rival political parties to work together for the sake of peace.
President Chandrika Kumaratunga and Prime Minister Ranil Wickramasinghe are engaged in a bitter dispute over the control of monies from the national lottery.
The row led to talk of snap polls creating a renewed sense of political instability.
Despite Ms Rocca's appeal, President Kumaratunga has told the Mr Wickramasinghe she has no intention of returning control of the lottery to him.