WASHINGTON (Reuters) - U.S. Trade Representative Jamieson Greer told lawmakers on Tuesday that not all of the agency's proposed multimillion-dollar fees for Chinese-built ships to dock at U.S. ports will be implemented, and they may not be cumulative.

Greer told a Senate Finance Committee hearing that the proposals were made to address a lack of shipbuilding in the United States, and that USTR would take time and listen to stakeholders to ensure that it gets the incentives right.

He said the port fees were "proposed actions or series of potential revenue" that could be used to incentivize shipbuilding in the United States.

"They're not all going to be implemented. They're not all going to be stacked," Greer said.

U.S. steelmakers and the industry's unions praised the proposal but were outnumbered by opponents.

Farmers, energy producers, chemical and construction companies, and domestic vessel operators testified in hearings in March that the plan would saddle them with costs that could put them out of business.

At the same time, domestic port operators warned the fees could spark supply chain chaos reminiscent of the early days of the COVID-19 pandemic.

Maritime experts and attorneys said the language in the proposal published in February is vague.

Among other things, they said the fees - which apply to China-based operators, fleets with ships built in China and operators with prospective orders for China-made vessels - could be cumulative and in some cases could reach $3.5 million per port call.