By Yuka Obayashi

TOKYO (Reuters) - Worries over U.S. President Donald Trump's protectionist policies are "growing every day", a senior executive at Nippon Steel & Sumitomo Metal Corp <5401.T> said, however, any impact on its U.S. steel exports would be limited.

Trump has threatened to ditch the North American Free Trade Agreement (NAFTA) that opened trade between Mexico, the United States and Canada. Dumping NAFTA could impact Nippon Steel's mill in Mexico that supplies Japanese carmakers - including Toyota Motor <7203.T> - that have plants there as well.

"We had some concerns over his protectionism comments even before his inauguration, but worries are growing every day to be honest," Toshiharu Sakae, executive vice president at Nippon Steel said on Thursday.

But any impacts on its own business may be limited because of the small volume of its exports to the United States, he said, pointing to 800,000 to 900,000 tonnes (a year).

"Also, what we export are pipes and rails that are not easily made by many local companies. Therefore direct impact will be small," he said.

Japan's top steelmaker is more worried about the potential indirect impact from any changes to U.S. import taxes and NAFTA. Nippon Steel supplies materials to Japanese automakers who export 1.6 million vehicles to the United States and who send about half of their output in Mexico to the U.S. market.

Sakae's comments were made in an earnings news conference after the world's No.3 steelmaker by crude steel output in 2015 reported a 41 percent drop in recurring profit to 108.5 billion yen ($963 million) for the April to December period, hurt by a surge in prices of coking coal, a main steel-making ingredient.

Coking coal futures <SCAFc1> on the Singapore Commodity Exchange more than tripled to $299.87 on Nov. 30, compared with $86.92 a tonne on June 1.

They have since dropped by about 40 percent to around $170 a tonne, but are still about double what they were in the middle of last year.

"We expect coking coal prices to stay between $150 and $200 per tonne for a while," Sakae said.

The company raised its full-year net profit estimate by 33 percent to 80 billion yen, helped by strong earnings on its overseas units, offsetting an extra cost from a fire at its Oita plant last month.

Its crippled Oita plant will cut its recurring profit by 10 billion yen and cost another 10 billion yen for repair, which will be counted as an extraordinary loss.

The company stuck to its full-year recurring profit forecast of 130 billion yen, in line with a consensus estimate of 133 billion yen from 16 analysts polled by Thomson Reuters I/B/E/S.

(Reporting by Yuka Obayashi; Editing by Christian Schmollinger and Tom Hogue)