WASHINGTON (REUTERS) - The United States and China may be in the final weeks of discussions to hammer out a deal to ease their tit-for-tat tariffs dispute, US Trade Representative Robert Lighthizer said on Tuesday (March 12).

Washington and Beijing have slapped import duties on each other's products that have costs the world's two largest economies billions of dollars, roiled markets and disrupted manufacturing and supply chains.

The US government is pressing for an end to practices and policies it argues have given Chinese firms unfair advantages, including alleged subsidising of industry, limits on access for foreign companies and theft of intellectual property.

"Our hope is we are in the final weeks of having an agreement," Lighthizer, the top US trade official, said during a US Senate Finance Committee hearing on Tuesday, though he cautioned that major issues remained.

"If those issues are not resolved in favour of the United States, we won't have a deal."

Lawmakers pressed Lighthizer for details on whether the Trump administration intends to keep its tariffs in place to ensure China is complying with any agreement.

President Donald Trump has vowed to rebalance the global trading system in favour of the United States as part of his "America First" policy.

"The focus of the negotiation from the Chinese side is the removing" of the US tariffs, Lighthizer said. "If that is a concession, that is something that is under debate."

The United States is addressing structural issues over intellectual property rights "with precision" in the talks and is nearing a deal to address currency manipulation, he added.

Progress in talks last month drove the White House to indefinitely delay hiking tariffs on US$200 billion (S$270 billion) worth of Chinese imports that were set to kick in on March 2. That led to mounting expectations a deal was in the offing, though Trump officials said on Friday another face-to-face meeting was not yet scheduled.

Lighthizer and China's top trade negotiator, Liu He, spoke on Tuesday, China's state media reported, and the US trade representative said during the Senate hearing that he had another call scheduled on Wednesday.

"We are working more or less continuously," Lighthizer said.

WTO PLAYBOOK

Lighthizer defended the Trump administration's actions to pressure other countries for reforms of the World Trade Organisation, saying at the hearing that the United States is working "diligently" to negotiate new rules for the world body.

Those remarks are the first from Lighthizer since the Trump administration filed its latest salvo at the WTO earlier this month, saying the United States would not allow the international body to dictate trade policy and defending the US use of tariffs to pressure trade partners, including China.

US officials have argued for years that WTO judges have routinely exceeded their mandates, imposing new obligations on members.

The "WTO is still largely operating under the same old playbook from the early 1990's," Lighthizer said in prepared remarks on Tuesday.

Lighthizer added that the US has pursued reforms "not to hurt the WTO - but to ensure that it remains relevant to a rapidly changing world," he said.