* Brazil court orders closure of Port of Tubarão
* After sharp gains, futures come off highs
* Caution remains as weak demand, oversupply weigh (Adds latest physical iron ore assessment from TSI)
By Ruby Lian and Manolo Serapio Jr
SHANGHAI/MANILA, Jan 22 (Reuters) - Iron ore futures in China and Singapore rose on Friday after the closure of a major Brazilian port halted shipments by top iron ore miner Vale SA VALE5.SA , offering some relief to an over-supplied market.
Unless the closure of the Port of Tubarão stretches to a week or more, however, the boost to iron ore prices may be short-lived with demand from top buyer China - already curbed by a slowing economy - seen limited ahead of next month's Lunar New Year holiday, traders and analysts said.
Iron ore futures came off session highs, underlining the still weak market sentiment.
A Brazilian federal court on Thursday ordered the suspension of activities at Vale's Port of Tubarão until pollution concerns were fixed, halting the miner's ability to ship more than a third of its output. 101.3 million tonnes of iron ore were shipped from the port to buyers globally in 2015, according to a source who tracks shipments in Tubarão. That's nearly 11 percent of China's total iron ore imports last year.
Vale is already under increasing pressure over its environmental record after a dam burst at a Brazilian mine run by its Samarco joint venture in October, killing at least 17 people.
"This will definitely boost prices in the short term. Vale has already cut shipments this month, and the port closure means it will further reduce shipments," said Li Xiaodong, analyst with Zheshang Futures in China's Hangzhou.
There has been no disruption so far in terms of shipments from Brazil, traders said, where cargoes take up to 40 days to reach China.
"If it lasts a week or more, there's a chance for Vale to declare force majeure," said an iron ore trader in Shanghai who sells Brazilian cargoes.
A force majeure declaration means delivery contracts do not have to be filled in their agreed time frame. There was no immediate response from Vale to a Reuters email on the impact to shipments.
UNSUSTAINABLE?
Open interest on the most-active May iron ore contract DCIOcv1 on the Dalian Commodity Exchange rose 84,122 lots to 1.51 million lots by close. The increase on positions eased from morning trade as prices cut gains.
Dalian May iron ore closed up 0.5 percent at 315.50 yuan ($48) a tonne after rising as high as 324 yuan, a two-week high.
On the Singapore Exchange, the most-active March contract SZZFH6 was up 2.9 percent at $38.40 a tonne at 0707 GMT, after jumping as much as 6.9 percent earlier.
Iron ore for delivery to China's Tianjin port .IO62-CNI=SI rose 2 percent to $41.30 a tonne on Friday, according to The Steel Index.
"It's an important port for (Vale). If they can't push iron ore through it then that will severely impact their client deliveries," said Daniel Hynes, senior commodity strategist at ANZ.
But immediate supply to China is unlikely to take a hit with more than adequate stocks at its ports, at nearly 95 million tonnes last week SH-TOT-IRONINV , and demand slow while the global market remains over-supplied.
"The rally may not be able to sustain for long, as demand is fading before the Chinese New Year," said an iron ore trader in the coastal Chinese city of Rizhao, referring to the Feb. 8-12 holiday.
"The market isn't too concerned with these short-term supply issues. They want to see permanent closure of capacity," said ANZ's Hynes.
Rebar and iron ore prices at 0707 GMT
Contract
Last
Change Pct Change SHFE REBAR MAY6
1823
+10.00
+0.55 DALIAN IRON ORE DCE DCIO MAY6
315.5
+1.50
+0.48 SGX IRON ORE FUTURES FEB
40
+1.10
+2.83 THE STEEL INDEX 62 PCT INDEX
40.5
-0.60
-1.46 METAL BULLETIN INDEX
41.29
-0.32
-0.77
Dalian iron ore and Shanghai rebar in yuan/tonne Index in dollars/tonne, show close for the previous trading day ($1 = 6.5794 Chinese yuan)