The U.N.’s top telecommunications overseer sought Monday to quell worries about greater Internet controls emerging from global talks in Dubai, but any attempts for major Web regulations will likely face stiff opposition from groups led by a high-powered U.S. delegation. …

Some at the Dubai conference, including a 123-member U.S. delegation with envoys from tech giants such as Google Inc. and Microsoft Corp., worry that any new U.N. oversight could be used by nations such as China and Russia to justify further tightening of Web blocks and monitoring. …

The agenda for the gathering of more than 1,900 participants from 193 nations covers possible new rules for a broad range of services such as the Internet, mobile roaming fees and satellite and fixed-line communications. Questions include how much sway the U.N. can exert over efforts such as battling cyber-crimes and expanding the Internet into developing nations.