The mayor of Warsaw, Lech Kaczynski, won Poland's presidential runoff on Sunday, partial results showed, sealing the rise of a party headed by his twin brother that pledges to uphold Roman Catholic values and strong welfare state protections.

With 91 percent of votes counted, Kaczynski led a pro-market legislator, Donald Tusk of the Civic Platform party, 54.5 percent to 45.5 percent. Final results were expected Monday.

Kaczynski claimed victory and signaled he was ready to reach out to Tusk's party after the hard-fought election.

"Polish society, despite all its divisions, must become one as soon as possible," Kaczynski said.

Kaczynski overtook Tusk by convincing older and poorer voters that he would protect the social safety protections that have eroded somewhat in the 16 years since the collapse of communism. Also crucial for voters in Poland -- homeland of the late Pope John Paul II -- were Kaczynski's promises to preserve Catholic values, such as current bans on abortion and gay marriage.

Kaczynski would become half of an extraordinary power team at the highest levels of Polish politics -- his twin, Jaroslaw, heads their Law and Justice party, which won parliamentary elections Sept. 25.

The brothers, both former activists in the Solidarity trade union movement, won fame as child stars in a hit film, "Two Who Stole the Moon." But their resemblance became a political handicap, pushing Jaroslaw to abandon his claim to become prime minister in favor of Kazimierz Marcinkiewicz, a little-known party official.

The new president will play a critical role in deciding whether to stick with the outgoing government's plan to pull Polish troops out of Iraq by early next year. Both candidates' parties have suggested that Polish forces could stay longer if the United States promised more financial aid. Poland's deployment of about 1,500 soldiers is deeply unpopular in the country.

Winner Lech Kaczynski, who campaigned on Roman Catholic values and safety net protections, indicated he would reach out to his rival's party.