The European Union joined a chorus of international voices demanding an end to Sri Lanka's two-week-old political crisis Friday, saying the island nation's international reputation and investments were at risk.
Wickremesinghe is holed up in his official residence refusing to go, saying his removal would be illegal, while Rajapakse is running a parallel administration from the prime minister's office.
President Sirisena has suspended parliament until next Wednesday as he and Rajapakse try to gather enough support among lawmakers to vote Wickremesinghe out, an effort that looks to be failing.
Amid rumours that Sirisena may seek to delay matters further, the EU, in a joint statement with Norway and Switzerland, said that parliament should vote "immediately when reconvened".
"Any further delay could damage Sri Lanka’s international reputation and deter investors," the statement said.
The United States, the United Nations and several other countries including Australia have also urged Colombo to end the unprecedented power struggle and restore confidence.
Wickremesinghe late Thursday thanked his supporters and urged them not to give up.
"In extraordinary numbers and with extraordinary courage you came out on to the streets, you spoke out," Wickremesinghe said in a video message posted on Facebook.
"You have not let this country be plunged into the darkness of dictatorship. For this inspiring effort, I want to thank everyone who has risen to fight for democracy and justice," he said.
His supporters staged a noisy cavalcade of motorcycles, auto-rickshaws, cars and vans in the capital Colombo on Thursday.
The power struggle on the island of 21 million people has paralysed much of the administration, according to legislators on both sides of the dispute.
Sirisena has filled only 22 of 30 cabinet positions -- purposefully keeping some jobs vacant to tempt legislators of Wickremesinghe's party to defect to Rajapakse's side.
According to latest counts, Wickremesinghe has 103 MPs after gaining a defector on Tuesday, while Rajapakse and Sirisena have 101. Most of the remaining 21 MPs are set to oppose Rajapakse, observers say.