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Under the watch of a Border Patrol agent, U.S. and Mexican pastors set up two small altars -- one on each side of a towering border fence -- for their Sunday service that spans two countries.

The priests then break bread simultaneously and hold up their challises to the tightly woven metal barrier. The guitar player is in Mexico, strumming a song led by clergy on the U.S. side. The buzzing of a passing Border Patrol officer on an all-terrain vehicle interrupts the music.

The religious service is one of myriad ways that life is seeping across the border post 9/11 as Congress considers spending billions on further fortification.

Ranchers, deputies and lawmakers from border states have long pleaded for federal help, saying their areas were overrun by people entering the U.S. illegally and armed smugglers.

But today there is growing opposition along the nearly 2,000-mile boundary to more agents and fences. They include U.S. ministers, business leaders and mayors who say those measures have reached their maximum effectiveness.

The crackdown in the past decade should be applauded for bringing detentions of illegal crossers to historic lows -- but ports of entry have been overlooked, said former El Paso Mayor John Cook, the director of the Border Mayors Association, representing U.S. and Mexican mayors.

Hours-long waits and overtaxed officers have become the norm at crossings, costing the region billions by deterring Mexican shoppers and delaying U.S. shipments, border mayors say. They favor expanding "trusted traveler" programs that give passes to pre-vetted crossers, digital fingerprinting and other technology to make ports of entry more secure, though Congress hasn't addressed those ideas.

"We don't need more Border Patrol agents -- we need more customs agents," Cook said. "Basically, we have 20th century infrastructure and for the most part, a 19th century policy, trying to facilitate trade in the 21st century."

A far-reaching bill passed by the Democratic-led Senate in June calls for an additional 20,000 Border Patrol agents, 700 miles of fencing and high-tech detection devices. The proposed measures are tied to overhauling laws to address illegal immigration, including providing a path to citizenship for some.

The Republican-controlled House favors tackling immigration with single-issue bills -- starting with border security. And Rep. Duncan Hunter, R-San Diego, said that long stretches of the border "remain dangerously open" and need fences. No action is expected until late fall, at the earliest.

While billions have gone into securing remote sections, the crossings lag behind the booming trade from the North American Free Trade Agreement, said Jerry Sanders, San Diego's former Republican mayor who now heads the San Diego Regional Chamber of Commerce.

He points to the San Ysidro port of entry, the world's busiest, where 50,000 cars and 25,000 pedestrians cross daily. The crossing has been under construction for years as Washington slowly releases money.

"Better infrastructure means better security," Sanders said.

The congressional debate comes as border communities have started reviving old ties.

San Diego's former Mayor Bob Filner, a Democrat, made that a hallmark of his term, before he resigned amid sexual harassment allegations.

He lobbied for the first binational Olympic Games in the region and opened a city government office in Tijuana.

The federal government also has started accommodating cross-border life.

In Texas, U.S. Customs and Border Protection officials in April re-established a remote crossing along the Rio Grande in Big Bend National Park where people arrive to the U.S. via a small boat and scan passports at a visitor's center.

The unmanned crossing was closed after the Sept. 11 attacks. It was reopened to comply with a decades-old bilateral agreement that formed a binational park by linking Big Bend to Mexican wildlands, said CBP spokesman Bill Brooks.

The isolated Mexican community, Boquillas del Carmen, depended on the boat crossing for tourism and getting supplies in Texas. Its population dropped after the crossing closed. Some are now moving back, Brooks said.

Federal authorities in San Diego County started giving access to the last of three border walls for a few hours on Sundays.

Families unable to leave the U.S. while their immigration status is in flux talked through the barrier with deported loved ones standing on the Mexican side.

On a Sunday in July, a teenage boy with a Dodger's cap and baggy jeans cried as he touched his father's fingertip through minute holes in the fence's metal screen.

The pastors prayed nearby.

Along the same stretch, Daniel Watman helped plant a garden with U.S. and Mexican volunteers in 2007 spanning both sides. Border Patrol officials ripped out the U.S. section in January 2009 to make way for another fence, he said. The section was replanted 10 months later but no one cared for the plants. Watman said he was handcuffed trying to tend to them.

Today arrangements have been made and the garden flourishes, but only volunteer caretakers are allowed in because of security restrictions.

"Life at the border is way more difficult than it needs to be," Watman said.