West Coast ports are bracing for a possible trade war with China, even as they hope for a summer boom.

A report last week by a task force at the Port of Oakland, which handles the bulk of international sea trade in the Bay Area, declared that future higher tariffs were a “wild card.” The port says it has seen little impact to date from the levies on steel, aluminum and agricultural products recently announced by the Trump administration and China.

“We’ve seen a peak season pattern of steady volume growth over the last three years,” John Driscoll, the port’s maritime director, said in a statement. “We expect that to continue in 2018, but we can’t be sure yet what will happen with international trade policy.” The port expects a 2 percent annual increase in containerized imports from August to October, typically the busiest period of the year.

According to government data, China accounts for 31 percent of imports and exports at the Oakland port, which handled $48.3 billion in trade last year and supports 73,000 local jobs.

This month, the administration announced a 25 percent tariff on $34 billion in imports from China to take effect July 6; an additional $16 billion could be subject to future tariffs. China announced its own retaliatory tariffs on a similar amount of U.S. exports to the country, which prompted President Trump to threaten possible sanctions on another $200 billion in Chinese goods.

The Port of Oakland said Thursday that it couldn’t immediately quantify the impact of those tariffs.

Despite the trade turmoil, major U.S. ports are expected to see record retail imports this summer, according to a monthly report prepared by the National Retail Federation and Hackett Associates.

July imports at a dozen ports including Oakland are forecast to rise 3.7 percent year over year to 1.78 million 20-foot equivalent units, or TEUs, the standard shipping measurement unit based on a 20-foot container.

“Despite an environment where the U.S. administration is enacting measures that could well lead to a trade war with most of its Asian and European trading partners, we see imports continuing to grow,” Ben Hackett, founder of Hackett Associates, said in a statement.

Other ports on the West Coast are trying to grapple with the tariffs’ effects.

The Port of Los Angeles, the country’s biggest container port, said Thursday that 15 percent of all cargo would be affected by the tariffs announced so far.

A Japanese ship carrying 20,537 metric tons of steel was stalled in San Francisco Bay for more than a month after tariffs on metals were enacted. It finally arrived at the Port of Stockton on June 13, the Record in Stockton reported.

Michael Zampa, a Port of Oakland spokesman, said no ships have been stalled there and numerous expansion projects are moving forward.

“The level of investment by business partners at the Port of Oakland is unprecedented. It reflects their confidence in the port’s long-term prospects,” Zampa said.

In August, developers Lineage Logistics LLC and Dreisbach Enterprises Inc. will open a $90 million, 280,000-square-foot Cool Port that will store perishable food shipments.

In April, China placed a 25 percent tariff on U.S. pork and 15 percent tariff on some fruits, which could affect some products to be handled by the new facility. Mexico also said this month that it would impose tariffs on pork. Pork is the third-largest category of exports handled by Oakland, according to WorldCity, a research firm that analyzes government trade data.

Developer CenterPoint Properties will start construction in July on the Seaport Logistics Complex, a 440,000-square-foot distribution center at the former Army Base in West Oakland. The port said it will be the largest warehouse building at a West Coast port. CenterPoint declined to comment on the effects of tariffs.

On an adjacent parcel controlled by the city of Oakland, Prologis, the San Francisco industrial property developer, has a new 256,000-square-foot warehouse building that’s seeking tenants.

“I don’t think we’re quite there yet, but any kind of trade war is bad for economic growth generally. And that will affect everything including our business,” Hamid Moghadam, CEO of Prologis, said in an earnings call in April. “We are not yet concerned by the action, and we’ll just see what the action is going to be.”

Roland Li is a San Francisco Chronicle staff writer. Email: roland.li@sfchronicle.com Twitter: @rolandlisf