Denver faces the largest security challenge in Colorado history when the Democratic National Convention comes to town because the event makes the city such an attractive terrorist target, security specialists say.

Members of the House Subcommittee on Intelligence, Information Sharing and Terrorism Risk Assessment stressed Friday that while keeping people safe will be an enormous job, doing it without infringing on their freedoms will be even more difficult - and just as important.

"Security and liberty are not a zero- sum game," said U.S. Rep. Jane Harman, D-Calif., who chaired the subcommittee's field hearing in Aurora. "You either get more of both, or less of both. Denver has a challenge but also an opportunity to show that this is a state, and this is a city, that gets it."

The 2008 convention is expected to draw 6,000 delegates, as many as 25,000 guests and 15,000 members of the media, said U.S. Rep. Ed Perlmutter, D-Colo., another subcommittee member.

"National special security events are a magnet for the media, and also for people who would do us harm," he said.

Most of the hearing focused on the importance of preventing attacks by improving and coordinating communication between federal, state and local law enforcement and security agencies.

Police from Denver and Aurora complained that since Sept. 11, 2001, getting access to critical intelligence has been more important - and more difficult - than ever.

"The more that information is made available regarding what the threat actually is, the better local law enforcement can act upon the intelligence," said Denver Deputy Police Chief Michael Battista.

The Secret Service will coordinate security through a 24-hour communications hub that links local and national law enforcement and public safety agencies, said Tim Koerner, Secret Service assistant director.

In 2005, Colorado created its own information-sharing network - the Colorado Information Analysis Center, or CIAC - to get critical intelligence to a wide range of local, state and federal agencies. CIAC works closely with the Rubicon Team, which monitors the vulnerability of the state's key infrastructure and resources.

"The CIAC acts as an early warning system for actual or suspected terrorist attacks, natural disasters and criminal activities," said James Wolfinbarger, director of the state Office of Preparedness and Security, which was created to detect and deter terrorism in the state.

Gov. Bill Ritter, who attended the hearing, said discussions are under way to make sure that the lines of communication are open and operating.

"We have to plan this so that everybody is communicating fully about the level of the threat, the breadth of the threat, and the individuals involved in it," he said.

Ritter agreed that while safety is paramount, it's also important to ensure that people's civil liberties are respected. Thousands of protesters are expected to show up, and police said last month that they probably will be allowed to rally within view of the Pepsi Center.

"I really think we have to get both security and liberty right," Harman said, "or we'll get them both wrong."