(Adds responses from hacking community)
By Andrea Shalal and Jim Finkle
DENVER/NEW YORK, May 24 (Reuters) - Washington is considering using visa restrictions to prevent Chinese nationals from attending popular summer hacking conferences in Las Vegas as part of a broader effort to curb Chinese cyber espionage, a senior administration official said Saturday.
The official said that Washington could use such visa restrictions and other measures to keep Chinese from attending the August Def Con and Black Hat events to maintain pressure on China after the United States this week charged five Chinese military officers with hacking into U.S. companies to steal trade secrets.
China has denied the charges, saying they were "made up."
Organizers of the two conferences said they knew nothing about any efforts under consideration by Washington, but that they believed limiting participation from China was a bad idea.
Jeff Moss, founder of both Def Con and Black Hat, could not be reached, although he posted his thoughts on Twitter: "First I have heard of it, boarding flight to D.C. now. I don't think it helps build positive community."
Chris Wysopal, a Black Hat review board member, said restricting access would have little impact. Hacking talks from both conferences are videotaped and sold on DVDs or posted on the web.
Members of the community of hackers and security professionals who present at Def Con and Black weighed in on Twitter. Responses ranged from bemusement to anger.
"That is terrible," said Richard Westmoreland.
"Racism by the U.S: No Chinese people allowed at Defcon," tweeted Valdes Nzalli.
"Something tells me that the Chinese hackers who the U.S. gov are worried about don't go to defcon anyways," said Steve Manzuik.
Def Con's official Twitter feed posted a tongue-in-cheek response: "If you are going to speak at or attend #DEFCON & you need a visa to enter U.S. please contact us for invite letter to help your app."
At Black Hat, an employee of Chinese security software maker Qihoo 360 is scheduled to speak on software vulnerabilities while two researchers with Chinese University of Hong Kong are set to talk on hacking social media. Def Con does not have any Chinese nationals on its roster.
It would be tough to prevent Chinese from attending Def Con because its privacy-conscious organizers only take cash and badges have no names.
U.S. agencies are weighing a range of options if China does not a curb its cyber espionage, said the official, who was not authorized to speak publicly.
"We've tried to have a constructive dialogue. The State Department and the Defense Department have traveled to China to share evidence of hacking by the (People's Liberation Army), but those types of interchanges have not sparked a lot of progress or reciprocity," said the official.
The possible visa restrictions were first reported by the Wall Street Journal. It said other options for increasing pressure include releasing new evidence about the alleged hacking operations.
Ten to 12 Chinese citizens were unexpectedly denied visas last week to attend a space and cyber conference hosted by the Space Foundation in Colorado this week, the organizers said.
Speakers included Director of National Intelligence James Clapper and other high-ranking U.S. intelligence and military officials.
State Department spokeswoman Jen Psaki said visa applications were confidential, but cautioned against drawing a connection between the denials and indictments of the hackers.
(Additional reporting by Jim Finkle in Boston and Lesley Wroughton in Washington; Editing by Stephen Powell, David Evans and Gunna Dickson)