The strike triggered by labor dispute in America's busiest ports of Los Angeles and Long Beach has lasted for the sixth day on Sunday without a solution, while lobbyists have pressured the White House to intervene.

The Port of Los Angeles, the nation's busiest container harbor facility, and second-ranked Long Beach together handled more than 400 billion dollars in goods arriving or leaving the West Coast by ship, according to Los Angeles port spokesman Phillip Sanfield.

In addition, the two ports directly or indirectly support roughly 1.2 million Southern California jobs -- workers involved in moving freight to or from the shipping complex. That does not count ancillary employment of people hired in restaurants, retail or other businesses that provide various services to those workers.

Combined, the Port of Los Angeles and the Port of Long Beach move 40 percent of all containerized trade in the country.

A national coalition of U.S. business groups is urging an end to the strike amid fears that a prolonged strike will cost the U.S. economy many billions of dollars. What's worse, it could even spread to the east coast.

Trade groups led by the National Retail Federation have sent letters to U.S. President Barack Obama and leading members of Congress, including California's two Democratic senators, Barbara Boxer and Diane Feinstein, asking them to intervene and help end the strike.

Those industry groups alleged that the strike has already cost 1 billion dollars a day to the U.S. economy.

The labor dispute has been triggered by 800 clerical workers at the ports, members of the Office of Clerical Union Workers. But they have the support of some 10,000 members of the International Longshore and Warehouse Union.

The strike, which started last Tuesday, has effectively shut down 10 of the two ports' combined 14 container terminals. Four other container terminals have remained opened, along with facilities for handling break-bulk cargo such as raw steel and tanker traffic.

The clerks had been without a contract for more than two years when labor talks with management broke off on Monday. The chief stumbling block has been the future of union representation for jobs that are lost through retirement.

Edward Wytkind, president of the Transportation Trades Department, AFL-CIO (TTD), issued a statement on the contract impasse between TTD member International Longshoremen and Warehouse Union (ILWU) Local 63 Office Clerical Unit (OCU) and the Los Angeles/Long Beach Harbor Employers Association.

"The Transportation Trades Department, AFL-CIO stands in full support of the 800 striking office clerical workers at the ports of Los Angeles and Long Beach who are waging a valiant battle to save good-paying jobs that drive our nation's economy.

"These workers have gone 30 months without a contract and are drawing a line against the steady and irresponsible outsourcing of their jobs to the lowest bidder. Too many transportation workers have seen their jobs disappear in an epidemic of outsourcing and cost-cutting that has weakened our economy and the middle class. We must not let that happen here.

"Instead of negotiating in good faith, industry representatives have asked the federal government to intervene in this legal strike. These efforts must be soundly rejected. Instead, management officials must negotiate a fair and balanced contract that will preserve these jobs now for future workers. Until that happens, we will stand solidly behind the working men and women of ILWU Local 63 who walk a picket line in the name of economic justice," the statement concluded.

The Harbor Employers Association said it has proposed "absolute job security," guaranteed full-time pay, wage increases and a one-time 3,000-dollar payment to each permanent employee to cover missed pay hikes in 2010 and 2011.

The proposal also calls for pension raises for the next two years and maintaining pension benefits for the following two years.

The employers have also agreed to give up full control over whether and when temporary employees are called in to work.

But the union is demanding that employers hire additional, unnecessary employees and is insisting on stronger restraints on the implementation and use of technology, after agreeing to back down on those demands, according to the Harbor Employers Association.