LONDON - Nickel and other base metals marched higher on Thursday after the U.S. central bank signalled rate cuts and investors hoped that the economy of top metals consumer China would recover.

Both nickel and copper touched the highest levels in more than three weeks, partly fuelled by speculators buying back bearish positions, traders said.

Metals got impetus after the U.S. Federal Reserve on Wednesday said the case for lower rates was building, suggesting it could ease monetary policy as early as next month.

Industrial metals were showing signs that they might extend the gains, but needed more good news, said Gianclaudio Torlizzi, a partner at consultancy T-Commodity in Milan.

"I'll remain with a cautious stance as long as base metals stay below their 200-day moving averages, which are the watershed levels," he said.

Nickel was the only metal on the London Metal Exchange that had breached that level, regarded as key by investors who use chart signals to guide their positions, he said.

"We need some more news to really turn bullish. We still have to see that the Chinese economy has really bottomed and is recovering," Torlizzi added.

Three-month nickel was the biggest gainer on the LME, climbing 2% to $12,335 a tonne by 1030 GMT, the highest since May 28.

* NICKEL BALANCE: In the first four months of the year, the global nickel deficit narrowed to 27,200 tonnes from a deficit of 59,400 tonnes in the same period of 2018, data showed.

* COPPER STRIKE: LME copper CMCU3 rose 1.1% to $5,983.50 a tonne, the strongest since May 28, as unions at Chile's Codelco were scheduled to discuss an improved contract offer that the world's top copper producer hopes will bring an end to a strike at its huge Chuquicamata deposit.

* ALUMINIUM OUTPUT: Global primary aluminium output rose to 5.438 million tonnes in May from a revised 5.222 million tonnes in April, data showed.

* DOLLAR: Metals got a boost after the dollar index sank and was on track for its biggest two-day drop this year following the Fed announcement, making dollar-denominated metals cheaper for holders of other currencies.

* TIN STOCKS/SPREADS: Tin spreads have eased after a big build-up in LME inventories MSNSTX-TOTAL , which have soared sevenfold over the past six weeks.

The premium of cash tin over the three-month contract has slid to $55 a tonne, the lowest since April and down from a peak of $320 on May 23.

* PRICES: LME aluminium CMAL3 gained 1.1% to $1,803 a tonne, climbing for a third straight day, zinc CMZN3 added 0.7% to $2,494.50, lead CMPB3 climbed 1.3% to $1,919 and tin CMSN3 advanced 1.9% to $19,260.

(Reporting by Eric Onstad; Editing by Jan Harvey) ((eric.onstad@thomsonreuters.com; +44 20 7542 7093; Twitter https://twitter.com/reutersEricO; Reuters Messaging: eric.onstad.thomsonreuters.com@reuters.net))