MOSCOW — As Ukraine’s new Parliament, firmly controlled by a coalition of pro-Western parties, convened for the first time on Thursday, President Petro O. Poroshenko urged lawmakers to repeal a 2010 law that codified the country’s nonaligned status in global affairs, and to instead pursue membership in NATO.

The Parliament, in two of its most important initial actions, chose Volodymyr Groysman, a close ally of Mr. Poroshenko, as speaker and also re-elected Arseniy P. Yatsenyuk, a technocrat well-loved in the West, as prime minister.

Mr. Poroshenko’s remarks were sure to antagonize Russia, which annexed Crimea in March and has supported violent, pro-Russian separatists in the eastern Ukrainian cities of Donetsk and Luhansk, in part because of the Kremlin’s opposition to any move by Ukraine toward NATO.

“Today it is clear that the nonalignment status of Ukraine proclaimed in 2010 couldn’t guarantee our security and territorial integrity,” Mr. Poroshenko told the Parliament. “This position has led to serious losses. That’s why we’ve decided to return to the course of NATO integration.”