* Barclays (LON:BARC) sees iron ore reverting to around $50/T by Q4
* But firmer steel prices seen remaining supportive
* Rio Tinto H1 profit more than doubles (Adds Rio Tinto results in final paragraph, updates prices)
By Manolo Serapio Jr
MANILA, Aug 2 (Reuters) - Iron ore futures in China retreated on Wednesday after a three-day rise that pushed prices to their highest in more than four months amid doubts a restocking-driven rally would be sustainable.
Chinese steel producers, the world's top buyers of iron ore, had been boosting stocks of the raw material as they increase output in anticipation of demand picking up after the summer lull but could leave them with too much iron ore later this year.
That has lifted spot iron prices this week to their strongest level since April at above $70 a tonne, although analysts at Barclays think that may be difficult to sustain, saying that a drop to "mid-to-low $50/tonne handle by the fourth quarter is increasingly likely."
"Even if we assume demand conditions remain supportive, we see the price outlook as still under downward pressure," they said in a note.
Iron ore for September delivery on the Dalian Commodity Exchange DCIOcv1 closed down 1.1 percent at 567.50 yuan ($84) a tonne. The contract rose to 582 yuan on Tuesday, its highest since March 24.
Spot iron ore prices already pared some gains on Tuesday, with the benchmark .IO62-CNO=MB slipping 0.2 percent to $73.56 a tonne, according to Metal Bulletin. It hit $73.70 on Monday, its highest since April 11.
But investment bank ANZ said firmer Chinese steel prices should "keep upward pressure on raw material prices in the short term".
The most-active rebar on the Shanghai Futures Exchange SRBcv1 closed 0.2 percent higher at 3,725 yuan per tonne. The construction steel product rose to 3,759 yuan on Tuesday, its highest level since September 2013.
Rio Tinto RIO.AX RIO.L , the world's No. 2 iron ore miner, on Wednesday reported that its first-half profit more than doubled to $3.94 billion amid a recovery in prices of iron ore and other commodities. = 6.7261 Chinese yuan)