Poland's acting president Bronislaw Komorowski is due to announce the date for fresh elections to replace Lech Kaczynski, who died in a plane crash in Russia at the weekend.
All 96 people aboard the Polish government jet, including Mr Kaczynski's wife Maria, and top-ranking officials, perished when the plane came down in heavy fog while trying to land in the Smolensk region on Saturday.
They had been travelling to attend a memorial service for Polish military officers and others killed en masse by Stalin's secret police at Katyn in 1940.
A third flight recorder has been found at the crash site and will be analysed in Poland.
The vote to elect a new president has to take place by July this year.
Before the crash, Mr Komorowski, the parliamentary speaker, was expected to run against the late president as the official candidate of Prime Minister Donald Tusk's governing Civic Platform Party, the BBC reports.
There is speculation that Jaroslaw Kaczynski, twin brother of Lech Kaczynski, may now stand in the late president's place.
Meanwhile, preparations are under way for the state funeral to be held in the city of Krakow on Sunday.
The bodies of Mr Kaczynski and his wife are lying in state in the capital Warsaw.
World leaders including United States president Barack Obama, Russia's Dmitry Medvedev and France's Nicolas Sarkozy are expected to attend.
New Zealand will be represented by Governor-General Sir Anand Satynand.