Copper prices edged lower on Wednesday as worries about weak demand in China and rising inventories balanced a slide in the dollar.

Three-month copper on the London Metal Exchange (LME) was down 0.4% at $9,627 a metric ton at 1430 GMT after a 1.5% drop on Tuesday.

Copper moved into positive territory after the dollar index tumbled to a four-month low, with other metals also gaining ground.

The dollar move was largely because of a surge in the yen that traders suspected was the result of yet another intervention from Japanese authorities.

A slide in the dollar makes commodities priced in the U.S. currency less expensive for buyers using other currencies.

But later, copper moved back into the red amid persistent concerns about lacklustre demand in top metals consumer China, he added.

Investors were awaiting policy news from the ruling Communist Party's "Third plenum", which is due to end on Thursday, after weak economic data from the world's second-largest economy.

"All the (stimulus) measures so far have been around the fringes. The Chinese government needs to engage in more domestic policy support," said WisdomTree commodity strategist Nitesh Shah. Some traders were doing so-called relative value deals, buying gold, which hit a all-time high, and selling copper, Al Munro at Marex said in a note.

Also weighing on copper prices have been rising inventories, highlighting excess supply in the market. LME stocks have nearly doubled since the start of June, climbing to their highest since September 2021.

Lead was the biggest gainer on the LME, advancing 0.9% to $2,204 a ton after data on Wednesday showed that available, or on-warrant, LME inventories slid by 18,675 tons to a one-month low.

Among other metals, LME aluminium added 0.4% to $2,414.50 a ton, zinc dropped 0.7% to $2,865, nickel eased 0.3% to $16,550 and tin dipped 0.2% to $33,115.

(Reporting by Eric Onstad Editing by David Goodman, Alexandra Hudson)