Klaus commands widespread support in public opinion polls, but the president is elected by a majority vote in a joint session of the 200-seat lower house and 81-seat senate, not the public.
Parliament must begin to meet to elect a new president 30 days before Klaus's term expires on March 7, 2008.
Klaus has little say in the day-to-day running of the country, but wields the power to appoint figures such as the prime minister, senior judges and central bankers.
He played a key role in the months following an inconclusive general election last June, though his political manoeuvring may have cost him votes both from the Civic Democrats of Mirek Topolanek, the country's prime minister, and the Social Democrats.
Jiri Paroubek, leader of the Social Democrats, said on Tuesday his party was likely to nominate its own candidate.
The government has a solid majority in the senate, but holds only 100 seats in the lower house, meaning Klaus will need support from at least one deputy from either the Social Democrats of the Communists.
Klaus replaced his rival Vaclav Havel, who had served two consecutive terms after Czechoslovakia split into independent Czech and Slovak republics in 1993.