SAN DIEGO - Standing in front of a warehouse where a tunnel running under the border was discovered in January, a group of Republican congressmen announced Wednesday tough new border security measures signed into law by President Bush.

The $21.3 billion Department of Homeland Security Appropriations Act, signed Wednesday by the president, includes money to hire 1,500 additional U.S. Border Patrol agents, build more border fencing and add 6,700 detention beds. The act also makes it a crime to dig tunnels under the nation's borders.

"Today's bill signing is an important step (to) have a more secure southern border," said Rep. Jim Sensenbrenner, R-Wisc.

More than two tons of marijuana were found inside the tunnel, which ran about 2,400 feet from a warehouse near the airport in Tijuana to a warehouse in an industrial neighborhood in Otay Mesa. Authorities have discovered more than 39 secret tunnels on the U.S.-Mexico border since Sept. 11, 2001.

Under provisions of the new law, those who build these tunnels could face up to 20 years in jail for building or financing them.

The press conference held in Otay Mesa about a quarter of a mile from the border also included North County congressmen Darrell Issa, R-Vista, and Brian Bilbray, R-Carlsbad, who are among many Republicans making illegal immigration a key campaign strategy to keep control of the House and Senate in November's midterm elections.

Immigrant rights groups called the new measures a ploy to mask Congress' failure to pass comprehensive immigration reform. The House and Senate passed widely differing reform bills, but leaders failed to agree on a compromise legislation.

"This is what passes for political leadership?" asked Frank Sharry, executive director of the National Immigration Forum, an immigration advocacy group. "A fence to nowhere with funds from nowhere?"

The congressmen deflected such criticisms, saying that border fences work. Bilbray said the stretch of border between Tijuana and San Diego, one of the major routes for illegal immigrant traffic, was once a lawless and violent area. Most of the traffic moved east of San Diego towards the mountains and deserts when the fence was built, Bilbray said.

"Even with a very primitive fence that we have at the Tijuana River Valley, it has made a major transformation," he said. "It ended up moving people to the east, but if they are trying to move away from where the fence is, then the fence is working."

Bilbray said he would like to see a fence across the entire 2,000 mile border with Mexico, "if that's what it takes" to stop illegal immigration. Thus far, the Congress has approved an additional 700 miles of fence.

Sensenbrenner said the $1.2 billion earmarked for fencing under the appropriations bill would pay for about 100 miles of fence. It would also increase the number of agents by 1,500 to a total of 14,800.

Since the mid-1990s, the federal government has built about 14 miles of fence along San Diego County's border with Mexico. But critics say enforcement efforts, including more agents, lighting and areal vehicles, have done little to stem the flow of illegal immigration into the country.

The Pew Hispanic Center, a nonpartisan research organization, estimates that an average of about 700,000 to 850,000 illegal immigrants come into the country each year, including people who cross the border illegally and those who come legally with visas and overstay when their permits expire.

Immigration officials say border enforcement efforts along Texas, Arizona and California, including Operation Gatekeeper in San Diego County, helped reduce the number of attempted crossings in the areas. But critics say they have simply diverted the illegal immigrant traffic to other more treacherous parts of the border.

The more dangerous routes have claimed the lives of 4,000 immigrants, said Claudia Smith, a long-time immigrant rights advocate who said more fences would only push people to more desolate areas.

"Until we address the structural causes of migration, including how particular trade policies of ours help drive it, migrants from south of the border will continue to try going over, under and mostly around a fence," Smith said.

- Contact staff writer Edward Sifuentes at (760) 740-3511 or esifuentes@nctimes.com.