SYDNEY, July 25 (Reuters) - Chinese iron ore futures broke a 3-day losing streak on Tuesday, showing modest gains at the start of trade as investors refocused on China's robust steel sector and as some of the world's biggest suppliers struggle to meet output guidance.
Australia's Fortescue Metals Group is expected to meet the low-end of forecast fiscal 2017 iron ore output of 165-170 million tonnes when it releases data on Thursday, due to bad weather in the second-half of the year at its mines.
That follows guidance warnings from Brazil's Vale and Australia's Rio Tinto over full-year output.
Iron ore on the Dalian Commodity Exchange was up 1.27 percent at 516.5 yuan ($76.53) a tonne.
The most active rebar on the Shanghai Futures Exchange gained 0.46 percent to 3,224 yuan.
Iron ore for delivery to China's Qingdao port .IO62-CNO=MB was also higher at $62.80 a tonne, according to Metal Bulletin.
China's giant steel sector churned out 72.78 million tonnes in June, equivalent to annualised production of 891 million tonnes, data last week showed.
But traders warned that high inventories of steel could cap steel and iron ore gains in coming weeks if they persist.
Stocks of rebar SH-TOT-RBARINV added 2.34 million tonnes over the last week to 372.7 million tonnes, according to SteelHome data.
$1 = 6.7488 Chinese yuan renminbi Reporting by James Regan; Editing by Joseph Radford