* Shanghai rebar jumps as much as 5.3 pct, Dalian ore 4.7 pct
* China vows to quicken steel capacity cuts
* BHP sees iron ore price jump as temporary
* Morgan Stanley (NYSE:MS) sees iron ore pullback to $40/tonne (Adds China's capacity cuts, BHP comment, updates prices)
By Manolo Serapio Jr
MANILA, Aug 16 (Reuters) - Chinese steel futures rallied more than 5 percent to their highest since April on Tuesday, lifting raw materials iron ore and coke, as infrastructure-driven demand extended gains in steel prices.
Steel also rose after China's economic planner vowed to accelerate the reduction of production capacity in its bloated steel sector, which would limit available supply. steel-intensive infra-programs have needed a higher-than-expected steel output rate from its industry, underpinning ore demand," Morgan Stanley analysts said in a report.
That is creating upside risk to Morgan Stanley's iron ore forecast of $40 a tonne for the second half of the year, the analysts say.
"Our short-term forecast still features a September/October seasonal pullback as China's steel demand and production rate abates ahead of winter, undermining ore demand/prices too," they said.
The most-traded rebar, a construction steel product, on the Shanghai Futures Exchange SRBcv1 climbed as high as 2,687 yuan ($405) a tonne, its strongest since April 25, before closing at 2,648 yuan, up 3.8 percent.
Chinese traders have been building steel stockpiles for weeks now to feed demand and to replenish a decline in inventories to multi-year lows.
Stocks of rebar at 28 major Chinese cities rose 2.8 percent from the prior week to 3.6854 million tonnes as of Aug. 12, according to data tracked by SteelHome consultancy. SH-TOT-RBARINV
Rebar stockpiles dropped to 3.4235 million tonnes in mid-July, the lowest since at least December 2011.
On the Dalian Commodity Exchange, iron ore for delivery in January next year DCIOcv1 jumped 3.9 percent to end at 438 yuan per tonne, after hitting a session peak of 441.50 yuan.
Other steelmaking ingredients also rose, with coke DCJcv1 climbing 6.3 percent and coking coal DJMcv1 gaining 1.8 percent.
Firmer futures should boost bids for physical iron ore cargoes to China, traders said, and strengthen the spot benchmark again.
Iron ore for delivery to China's Tianjin port .IO62-CNI=SI slipped 0.3 percent to $60 a tonne on Monday, according to The Steel Index. The spot index, up 40 percent this year, touched a three-month peak of $61.40 on Aug. 8.
BHP Billiton BHP.AX BLT.L Chief Executive Andrew Mackenzie said the current jump in iron ore prices is likely temporary, driven by stimulus in China and a slower ramp-up in iron ore production from the major miners. made the comment at a conference call after the world's No. 3 iron ore miner reported a record $6.4 billion annual loss. ($1 = 6.6335 Chinese yuan)