Talas said: "I genuinely congratulate Mr Christofias and I call on him to co-operate in the process of negotiations which should start as soon as possible."
Christofias, a communist who says he will not tamper with the island's market economy, secured victory in Sunday's run-off election on a wave of discontent with his predecessor's hardline policies towards Turkish Cypriots.
Jose Manuel Barroso, the European Commission president, said in a statement to Christofias: "I would strongly encourage you to grasp this chance and without delay start negotiations under United Nations auspices with the leader of the Turkish Cypriot community on a comprehensive settlement."
The US and Britain also issued statements saying 2008 offered a window of opportunity and offering support.
The Cypriot press hailed the day as historic, both because Christofias becomes the island's first communist president, the only one in the 27-member EU, and because it presents a significant opportunity to end the island's stalemate.
"After five wasted years ... he has a moral obligation to try to make up for lost ground," wrote the Cyprus Mail.
The island has been split along ethnic lines since 1974 when Turkey invaded after a brief Greek-inspired coup.
Reunification efforts broke down in 2004 when Greek Cypriots rejected a UN plan and a divided Cyprus joined the EU soon after.
The EU recognises the Greek-Cypriot government in the south, where voting took place on Sunday, while only Turkey recognises the breakaway north.
A UN team was expected on the island by early April to assess the potential for a settlement, diplomats said.