The Port of Los Angeles, the country's busiest seaport, said today that its June containerized volumes hit their highest monthly level since September 2012, with a nearly 14-percent year-over-year increase from June 2013 totals.

According to port data, Los Angeles handled 736,438 twenty-foot equivalent units (TEU) in June, up from 646,650 TEU in June 2013. Import volumes rose 16.6 percent from year-earlier levels. Export volumes increased 8.51 percent year-over-year.

Total loaded import and export containers rose 14.05 percent, while total "empty" containers increased by 13.4 percent, according to port data. So-called empties accounted for about 260,000 of the total containers that moved through the port in June, it said.

For the first six months of calendar year 2014, overall volumes rose 9.2 percent to 4.05 million TEUs. For the port's 2013-14 fiscal year, which ended in June, volumes increased 5.5 percent from the prior fiscal year.

The port handled 696,847 TEUs in June 2012, according to port data.

Phillip Sanfield, a port spokesman, said last month's strong import volumes were due in part to cargo entering U.S. commerce earlier than usual ahead of a possible labor strike or management lockout at West Coast ports. The International Longshore & Warehouse Union (ILWU) and ship management are bargaining over a new labor contract to replace a six-year compact that expired July 1. Both sides last week agreed to a three-day contract extension to allow the union to deal with a separate, long-running labor dispute in the Pacific Northwest.

Sanfield said there is no way at this time to quantify the role of labor concerns in influencing June's traffic data. "Perhaps we'll know more about the impact after July and August volumes come in," he said in an e-mail.

Sanfield added that volumes have increased as more mega-containerships have been calling at the port. In June, Los Angeles handled a 13,000-TEU vessel operated by the Chinese flag carrier COSCO Ocean Shipping Co. That is the largest vessel to ever call the port, Sanfield said.

In addition, 10 cranes have been raised in the past six months, a sign terminal operators expect to see an increase in the number of mega-containerships calling the port. Each crane has been raised by 30 feet and gives operators more width to maneuver across a ship's boom, enabling terminals to process more containers with greater speed and efficiency, according to Sanfield.

A report issued last week sent the clearest signal yet that U.S. importers have pulled orders and deliveries forward to avoid any labor-related service disruptions. Import volume at the largest U.S. ports in July will reach 1.5 million TEUs, the highest monthly levels at least since 2009 and perhaps since the data sets were created in 2000, according to a monthly forecast issued by the National Retail Federation (NRF) and consultancy Hackett Associates.

The report projects 1.51 million TEU imports will enter U.S. commerce in August. In May, the latest month for which final numbers are available, 1.48 million TEUs moved through the ports, up 3.7 percent from April and 6.6 percent from May 2013, the report said.

The report found that West Coast ports handled 59 percent of retail containerized cargo in May, down from 62 percent in January. This indicates that retailers are increasingly diverting freight to East Coast ports in an effort to steer clear of labor disruptions, the study suggested.