Washington’s top trade official on Tuesday said the United States and China were likely within “weeks” of ending their trade negotiations -- but a successful outcome was not assured.

“Our hope is that we’re in the final weeks of an agreement but I’m not predicting one,” US Trade Representative Robert Lighthizer said in Senate testimony.

“We can’t predict success at this point but we are working hard.”

Eight months into their sprawling trade war, US and Chinese officials have alternated between projecting optimism and warning that they have much to do before reaching a final outcome.

The two sides have exchanged tariffs on more than $360 billion in two-way trade, but Lighthizer on Tuesday declined to state publicly whether Washington would lift the tariffs it has so-far imposed if both sides reach a deal.     

Far-reaching changes from Beijing sought 

US officials are demanding far-reaching changes to Chinese industrial policy -- including an end to massive state intervention in markets, subsidies and the alleged theft of American technology -- and insist that any agreement be enforceable.

Lighthizer refused to say whether the United States planned to lift any existing tariffs as part of the current talks, but said Washington would reserve the right to impose them should China fail to keep up its end of the bargain.

“We have to maintain the right to be able to -- whatever happens to the current tariffs -- to raise tariffs in situations where there’s violations of the agreement,” he said.

“That’s the core. If we don’t do that, then none of it makes any difference.”

Democrats have accused President Donald Trump of going soft in the trade talks and moving toward a superficial agreement rather than tackling long-standing problems in trade with China.

But Lighthizer said Tuesday the agreement would either have teeth “or the president won’t agree to the agreement.”

During four rounds of shuttle diplomacy since December, officials announced that China had agreed to resume or increase purchase of US agricultural goods, with Trump announcing he would likely seal any deal at a “signing summit” with Chinese President Xi Jinping late this month.

But the White House has since said there is no date yet for such a meeting.