Top Chinese and US trade negotiators held "constructive" discussions over the phone on a preliminary trade deal between the two countries, China's commerce ministry announced in a statement on Sunday.

The long-running trade war between Washington and Beijing has weighed on the global economy and spooked markets, with the two sides imposing punitive tariffs on hundreds of billions of dollars in two-way trade.

US President Trump announced a "phase one" trade deal last month which has yet to be signed.

Vice Premier Liu He spoke with US Trade Representative Robert Lighthizer and Treasury Secretary Steven Mnuchin on Saturday, and had "constructive discussion on each side's core concerns regarding the phase-one agreement", the Chinese commerce ministry said.

The long-running trade war between Washington and Beijing has weighed on the global economy and spooked markets
The long-running trade war between Washington and Beijing has weighed on the global economy and spooked markets AFP / STR

The two sides will "continue to maintain close communication", it added, without providing further details.

Since October, differences between Washington and Beijing over whether, when and by how much to reduce tariffs on each other's goods have spilled out into the open.

Trump this month denied the Chinese commerce ministry's claim that the two sides had agreed to roll back existing tariffs as part of the deal, details of which have not been released.

Trump had planned to sign a pact with China's President Xi Jinping on the sidelines of the now-cancelled summit in Chile this month.

Since that cancellation, no other meeting between the two has been announced.

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