WARSAW, Poland — 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 officially invited to the ceremony in Parliament, but aide Pawel Gras told PAP agency that Tusk had no invitation from Duda and was "respecting" that decision.

In his early years as prime minister from 2007, Tusk had tense relations with then-President Lech Kaczynski, who co-founded Duda's opposition Law and Justice party. Tusk's absence could be a sign that Duda might have a hard time finding ways to work alongside the centrist government that Tusk led until becoming EU leader last year.

In his first speech as president, Duda, 43, promised to pay attention to the needs of the underprivileged. As supreme commander of Poland's armed forces, he said he was especially concerned about the nation's security in the face of a resurgent Russia.

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

He vowed to press for more NATO security guarantees at next year's alliance summit in Warsaw. He called his program Newport Plus, in reference to a summit in Wales last year that decided on a rapid reaction force in the region, which is still being formed. Duda insists that is not enough.

Within the European Union, he vowed to make a "correction" and speak with more authority on Poland's goals and needs, in order to make them clearer to political partners. He had previously suggested that Tusk's government had not done enough in the area.

The powers of Poland's president are limited to approving or rejecting legislation, proposing laws, which, however need to be backed by the lawmakers, and to formally representing Poland on 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.

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

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