The potentially explosive showdown on Friday has become the focus of global attention and concern.
The bitter political crisis not only saw President Chandrika Kumaratunga launch her own power bid, but the move threatened the peace Prime Minister Ranil Wickremesinghe built with Tamil rebels.
India has called for a quick solution and the International Monetary Fund warns the confidence in the economy could suffer.
These are just the latest in a series of international expressions of concern.
Crunch day will be Friday according to backers of Prime Minister Wickremesinghe who say they will cram the airport with his supporters for his arrival.
Odd couple: Wickremesinghe and
Kumaratunga are polls apart
He, in turn, will be armed with a fresh seal of approval for his peace overtures from the United States.
President Kumaratunga - who sacked three cabinet ministers, suspended parliament and declared a state of emergency this week citing security concerns - still insists she has acted in the nation's best interests.
She also said she backed the peace process despite the aggressive power play against her arch-rival.
The crisis is expected to come to a head with Wickremesinghe's scheduled arrival at 0200 GMT on Friday after meeting President George Bush in the White House.
He said there his foremost job was to keep the fragile peace with the Liberation Tigers of Tamil Eelam (LTTE) on course.
A ceasefire signed 20 months ago has given the island its longest respite since the separatist war broke out in 1983, but Kumaratunga accuses the government of conceeding too much to the LTTE, one of the world's most ferocious guerrilla armies.
Kumaratunga, who is elected separately from the prime minister, backed that up by invoking security concerns.
Her office said she "has only exercised her responsibility as the constitutional head of state in the greater interest of the sovereignty and the security of the nation."
"This was a gross abuse of presidential power. It is a reckless action. There is no violence, no security situation and no valid, proper reason to declare a state of emergency"
"The president is committed to the continuity of the ceasefire agreement and to keep open the channel of communication with the LTTE and to a negotiated settlement within a united country.
"The president assures the people of Sri Lanka that there is no cause for alarm or panic."
The statement came after Wickremesinghe's cabinet called on her to reconvene parliament and restore the portfolios of the sacked defence, interior and media ministers.
"This was a gross abuse of presidential power. It is a reckless action. There is no violence, no security situation and no valid, proper reason to declare a state of emergency," cabinet spokesman G.L. Peiris told a news conference.
The economy was already suffering, with tourists cancelling visits and investor confidence shaken, he said.
The state of emergency allows detention for up to one year without charge as well as widening Kumaratunga's powers and those of the military. It was used widely by previous governments to crack down on the Tamil rebellion.
The split between the president and prime minister has been looming since Wickremesinghe won parliamentary elections in late 2001, defeating Kumaratunga's party on a platform of pursuing peace with the Tigers.
Despite the crisis, Colombo was calm. There was increased buying of essential goods in Jaffna peninsula, the cultural homeland of the Tamils, but residents said that was caused by false rumours the sole highway to the north would be closed.
India and Japan both voiced concern for the second straight day about the impact the crisis was having on the peace process.
Kumaratunga sacked ministers
and suspended parliament
"The prime minister informed her that India was anxious about recent political developments and urged that a constitutional crisis be averted," an Indian Foreign Ministry official told Reuters after Kumaratunga spoke to Prime Minister Atal Behari Vajpayee by telephone.
Japanese Chief Cabinet Secretary Yasuo Fukuda said: "The government of Japan expresses its apprehension over the current developments in Sri Lanka, including the issuing of the state of emergency."
The IMF also called for a quick resolution. "We certainly hope that the present constitutional uncertainty is resolved quickly, so confidence, which has improved, is not eroded," IMF spokesman Tom Dawson told a regular news briefing.
Police and army officials said for the moment, security at the airport was not being increased for Wickremesinghe's return.
"We have no information that there are any demonstrations planned," said police official Chandra Fernando.