(Recasts, adds comment, changes dateline from Hanoi) LONDON, May 20 (Reuters) - Copper prices rose on Thursday as a softer dollar and worries about a strike in Chile spurred purchases, but plans by top consumer China to manage the supply, demand and prices of commodities capped gains. Benchmark copper on the London Metal Exchange was up 0.6% at $10,058 a tonne at 1041 GMT. However, prices of the metal used widely in power and construction are down 6% since hitting a record high at $10,747.50 a tonne earlier in May. “There’s been some buying on the back of a lower dollar and the possibility of a strike at Escondida (copper mine in Chile),” a copper trader said. “But the rally does seem to have to run out of steam.”