WASHINGTON — Vice President Joseph R. Biden Jr. opened annual strategic talks with senior Chinese leaders here on Wednesday by repeating the United States’ accusation that the electronic theft of American intellectual property could undermine the relationship between the world’s two largest economies.

And to no one’s surprise, the Chinese had an answer ready: that the publication of secret documents showing the extent of American surveillance of Chinese universities and other institutions undercuts the Obama administration’s case.

That friction, American officials conceded in private, underscores how difficult it will be for the United States to make progress on what President Obama and his top aides have said is now a central issue between two countries whose economies are intertwined and whose militaries are in competition.

And at a time when the Chinese economy is showing signs that it is headed into a period of slower growth, the administration’s hopes of persuading Chinese leaders to crack down on the daily barrage of theft and espionage over the Internet — considered crucial to keep China competitive — is likely to be even more difficult.