WASHINGTON — Violence along the border with Mexico will likely increase this year as the administration bolsters Border Patrol staff and adds more fencing and technology to catch illegal immigrants, Homeland Security Secretary Michael Chertoff said Tuesday.

Chertoff's comments came after the death Saturday of Border Patrol Agent Luis Aguilar in California. Aguilar, a 32-year-old father of two, was hit by a Hummer driven by suspected drug smugglers as he tried to place spike strips in front of the escaping vehicle.

Aguilar's death has drawn attention to escalating violence on both sides of the U.S.-Mexico divide. Chertoff and other administration officials said the violence that claimed Aguilar's life stems partly from heightened border security measures. And they said the agent's death highlights the need to continue initiatives such as a fence, which has drawn stiff opposition from some border residents and officials.

"Experience shows that the more successful you are in putting pressure on criminal organizations, the more violent they will become in fighting back," said Chertoff. "The sad, tragic fact is that the increase in violence is very consistent with other metrics we've had that show we're getting increased success with stopping the flow across the border."

In an interview with the Los Angeles Times and The Associated Press, Chertoff and Border Patrol officials said the agency considered the agent's death to be murder and was working closely with Mexico to investigate. Agency officials said it was the first murder of a Border Patrol agent since 1998. Mexican officials reportedly found the burnt Hummer in Mexicali.

Aguilar's death has also underscored the controversy about the administration's efforts on the border.

Several border groups have sharply criticized Homeland Security for wanting to build a border fence on private land. Many residents, mayors and business owners object to the plan as well as Chertoff's announcement that, if necessary, his agency will seize land from unwilling property owners to continue construction.

"I know it gripes some people; they don't want it on their property," Chertoff said. "But ... if the (Border Patrol) chief says to me building a barrier, building a fence would make it safer in this particular area, ... I'm going to use every available tool, including the courts."

Conservatives critical of President Bush's policies on immigration and the border drew a link between Aguilar's death and the sentencing of two Border Patrol agents who shot a Mexican drug smuggler. In the wake of Aguilar's death, these critics have renewed their calls for the pardon of Ignacio Ramos and Jose Compean.

The border agents shot the smuggler in the buttocks as he fled to Mexico. Prosecutors charged the border agents then tried to destroy evidence of the shooting. Despite the administration's prosecution of the agents, the men have become heroes to many conservatives.

Border officials strongly dismissed that allegation. "It's not a fair comparison, and it diminishes our shock and heartbreak," said National Deputy Chief Ron Colburn.

Chertoff said there was no indication Aguilar had time to defend himself. Both Colburn and Chertoff stressed Border Patrol agents are allowed to use force to defend themselves. Chertoff said Border Patrol agents have been attacked with everything from firearms to knives, bats, steel pipes, vehicles, boats and sling shots. Violence on the border increased 31 percent from 2006 to 2007 and attacks on agents jumped 44 percent over the same period.