The U.S. government gave American Internet providers addresses linked to suspected Chinese hackers earlier this year as part of a previously undisclosed effort aimed at blocking cyberspying, current and former U.S. officials said.

The push reflects a significant shift in levels of cooperation between the government and Internet companies amid rising concerns over hacking. It also marks a bold move by the U.S. as it takes part in high-level meetings on cybersecurity and other matters with the Chinese this week in Washington....