Andrzej Duda, Poland's new conservative president, takes office

In his inauguration speech, Duda, now the supreme commander of Poland's armed forces, said his chief concern was for the nation's security in the face of a resurgent Russia.

Conservative Andrzej Duda was sworn in as Poland's new president Thursday, bringing political change to the nation's top office. However, confusion surrounded the absence from the ceremony of European Union leader and former Polish prime minister Donald Tusk.

Some officials insisted Tusk had been invited to the ceremony, but aide Pawel Gras told PAP agency that Tusk had no invitation from Duda and was "respecting" that decision.

At the start of his time as prime minister, from 2007, Tusk had tense relations with then-President Lech Kaczynski, who co-founded Duda's opposition Law and Justice party. Later, the party accused Tusk of contributing to Kaczynski's death in a 2010 plane crash through lack of concern for the president's security.

Tusk's absence Thursday suggests that Duda might have a hard time working alongside the centrist government that Tusk led until becoming EU leader last year.

In his inauguration speech, Duda, 43, now the supreme commander of Poland's armed forces, said his chief concern was for the nation's security in the face of a resurgent Russia.

"We need a greater presence of NATO in this part of Europe and in our country," Duda said.

He vowed to press for more security guarantees at next year's NATO summit in Warsaw.

Within the European Union, he said Poland needs to speak with more authority about its goals and needs, in order to make them clearer to political partners.

The powers of Poland's president are limited to approving or rejecting legislation and proposing new laws. He formally represents Poland in the international arena.

Duda quit Law and Justice after winning the May elections, in a sign that he would be the president of all Poles. In his speech Thursday he appealed for mutual respect and cooperation.

Rafal Grupinski, a prominent lawmaker of the ruling Civic Platform, said that the president and the government — now coming from opposing political forces — will have to show a "maximum of good will" in order to cooperate.

Duda was sworn in before the National Assembly of lawmakers and senators at the Parliament, in the presence of the government, his predecessor Bronislaw Komorowski, and other former presidents, including Lech Walesa. Duda's wife, Agata, was by his side. His parents and daughter were also present.

Later he attended a special Mass at Warsaw's St. John Cathedral and was given authority over Poland's top state distinctions, or medals, at the Royal Castle.

Duda's May victory over Komorowski was a surprise, and a warning to the ruling coalition that it may lose power in October general elections. The reason seemed to be the dissatisfaction of many Poles who say they are not benefiting from Poland's economic success.