Members of Congress held coastal field hearings about immigration reform Wednesday on both U.S. coasts.

A Senate Judiciary Committee hearing in Philadelphia, Pennsylvania examined a proposal for a temporary guest worker program - a key provision in the Senate-passed immigration reform bill.

Under the Senate bill, some of the estimated 11, to 12 million illegal immigrants in the United States would have an opportunity to pursue a path to citizenship if they meet certain conditions.

A House-passed bill does not address the guest worker proposal or prospects for citizenship. Instead, it would strengthen border security and designate illegal immigrants as felons to be deported.

At the Senate hearing, New York City Mayor Michael Bloomberg said the economy of his city would collapse if the estimated 500,000 undocumented workers who provide critical services to city residents were deported.

"A lot of them provide elbow grease [work] to make the traditional industries you talked about - whether it is tourism-related industries of transportation and food and beverage or home health care or providing a lot of the cleaning services or driving the taxi cabs and those kinds of things," said Michael Bloomberg. "Without them the city could not survive the way it is."

On the other U.S. coast, in San Diego, California, a House subcommittee on international terrorism met to focus on border security.

Chief Border Patrol Agent for the San Diego sector, Darryl Griffin, testified that criminal cartels exploit the border and pose a significant threat to U.S. security.

He made his comments under questioning by Congressman Darrell Issa, a California Republican.

Issa: "Whether it is drugs or other contraband or people, they do not care; they normally operate in both industries."

Griffin: "That can be an occurrence, yes sir."

Issa: "Therefore, can I presume that they will take people or packages of stuff, they do not really care if there is a dirty bomb in there or an al-Qaida agent. Basically, they move people and bags of things, is that right?"

Griffin: "That would be a correct assumption."

As the congressional field hearings took place, immigration reform was also on President Bush's mind.

Speaking in Alexandria, Virginia, the President renewed his call for Congress to complete comprehensive immigration reform legislation that includes a guest worker proposal.

"I look forward to working with Congress for a temporary worker plan that will have background checks to make sure that people that are coming aren't criminals, that say you can come here for a temporary basis, that you can do work others are not doing, and that is one way to make sure that employers know they are hiring people who are here legally," said President Bush.

The House and Senate must reconcile differences in their two immigration reform bills before a final version is sent to President Bush for his signature. With both chambers so far apart on the issue, lawmakers acknowledge negotiations will be difficult.