REFILE-POLL-With China's economy under threat, iron ore prices seen sliding further

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* Spot iron ore seen averaging $61/T in H2 from $70 in H1 -poll

* Signs of slower Chinese economy, tariff row to pressure prices

* China, U.S. brace for additional tariffs on Friday

MANILA, July 2 (Reuters) - Signs of a slowing Chinese economy and risks from steep tariffs brought in during a festering Sino-U.S. trade row will curb demand for steelmaking material iron ore, pushing down its price 13 percent in the second half of 2018, a Reuters poll showed.

After setting a record pace in the first half of 2018, steel output in top producer China is seen easing over the next six months as domestic consumption slows and exports are restrained by a rising tide of protectionism.

Benchmark 62-percent grade iron ore for delivery to No. 1 market China <.IO62-CNO=MB> will average $61 a tonne in July to December, down from $70 in the first half of the year, according to the median estimate in a Reuters poll of 16 analysts.

Strong profit margins spurred China's steel production this year, reaching a record 81.13 million tonnes in May. But Chinese demand is likely to be reduced amid tighter credit and slower infrastructure investment.

"We expect a gradual slowdown in China's ... steel intensive sectors such as infrastructure and property. Consequently, steel demand should start to roll over and decline as 2018 progresses," said Carsten Menke, a commodity strategist at Julius Baer who took part in the poll.

Menke sees iron ore averaging $60 in the third quarter before easing to $57.50 in October-December.

"Growing global protectionism could accelerate the decline in production should more and more countries take measures to block Chinese exports," he said.

As China prepares to impose tariffs on hundreds of imported U.S. goods on Friday in response to the Trump administration's plan to slap duties on $50 billion of Chinese imports, other countries such as Canada are reportedly eyeing steel tariffs against China and other countries.

China's tariff war with the United States threatens to knock the world's second-largest economy, which already saw weaker-than-expected activity in May amid Beijing's prolonged crackdown on riskier lending that has lifted borrowing costs for companies and consumers.

Iron ore has fallen almost 11 percent this year to $65.02 a tonne on Friday, near a one-month low, reflecting a well-supplied market with stocks at Chinese ports near record highs despite disruptions including the suspension of Anglo American Plc's Minas-Rio mine in Brazil.

"The iron ore price cannot be bullish due to decreasing steel demand and increasing high grade iron ore supply," said Jeremy Platt from UK consultancy MEPS.

For details on the results of the poll, click

(Reporting by Manolo Serapio Jr.; Additional reporting by Sumita Layek in Bengaluru and Muyu Xu in Beijing; Editing by Joseph Radford)