In an episode that was also highly embarrassing to Mr. Tusk’s government, prosecutors raided the offices of Wprost last week and tried to seize the editor in chief’s laptop. The subsequent siege was broadcast on live television, and security agents were forced to leave empty-handed, though the newspaper later turned over copies of the taped conversations to the authorities.

“I am especially concerned about the lack of clarity as to who did the recordings,” said Andrew Michta, a professor of international studies at Rhodes College in Memphis, who has extensive experience in Central and Eastern Europe. “And also why they surfaced now, at a time of significant shifts in regional security, when Poland is making key decisions on defense, military modernization and working to increase U.S. and NATO military presence in the country.”

Rumors have been flying in Warsaw about who might be behind the electronic eavesdropping, which appears to have been underway for more than a year. Potential suspects include political enemies, disgruntled security operatives or Russian agents releasing the tapes now in reaction to Poland’s hard-line on Ukraine.

At first, Wprost would not say how it had obtained the recordings, but on Sunday it said that the tapes had been provided by a “businessman.”

Aleksander Smolar, the president of the Stefan Batory Foundation, which advocates for open government and civic issues, said the timing of the conversation was critical to understanding the comments in it.

While still maintaining a strongly pro-American position, Poland’s top officials had worried in recent years about the United States’ interest in deepening its commitment to regional security. But Russia’s annexation of Crimea turned that attitude around, Mr. Smolar said, as shown by President Obama’s warm reception in Warsaw this month.

Mr. Sikorski’s comments, if they are accurately depicted in the excerpt, were a reflection of that earlier frustration, Mr. Smolar said.