UPDATE 3-Nippon Steel says on track to close US Steel deal by Sept

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Deal has faced opposition from some US lawmakers, union

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Nippon Steel April-December net profit down 14.7%

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Raises FY net profit forecast to Y470 bln yen from Y420 bln

(Rewrites with quotes, detail)

By Yuka Obayashi and Katya Golubkova

TOKYO, Feb 7 (Reuters) - Japan's Nippon Steel is on track to finalise its planned $15 billion acquisition of U.S. Steel by the end of September as it steps up talks with key stakeholders, particularly labour unions, an executive said on Wednesday.

The deal by the world's No.4 steelmaker to buy U.S. Steel has drawn criticism from some Democratic and Republican U.S. lawmakers and the powerful United Steelworkers (USW) union.

Former U.S. President Donald Trump, whose protectionist "America First" policies were a hallmark of his term in office, has said he would "instantaneously" block the deal if he won the Nov. 5 election.

In a bid to close the deal by September as scheduled, Nippon Steel is stepping up talks with various stakeholders, Executive Vice President Takahiro Mori told a news conference on Wednesday.

Last month, Mori met U.S. Congress members "to discuss how the deal will be beneficial to all stakeholders, including American industry and workers".

"I don't think they can block a project that is meaningful to both sides, and beneficial to related industries and both countries, simply because of political considerations," Mori said, adding the company had hired U.S. lobbyists.

Nippon Steel aims to gain consent from the USW, the main union at U.S. Steel, by emphasising the deal would strengthen the U.S. company's profitability and finances, leading to stable employment.

Both companies are also pursuing regulatory approvals required in the U.S. and other jurisdictions.

U.S. Steel, which would become a wholly-owned unit of Nippon Steel, could have a shareholder meeting at end of March, at around which time Nippon Steel wants to reach an agreement with the labour union, Mori said.

If either side terminates the deal, it is obliged to pay a penalty of $565 million to the other.

Nippon Steel, which has secured a bridge loan of $16 billion for the deal from Japanese banks, plans to select the best financing method among various options including equity finance, Mori said.

The challenges the acquisition faces in the United States, Japan's closest ally and where Tokyo is the biggest foreign investor, have rattled Japanese companies, which analysts say could now become more cautious when sizing up U.S. deals.

Nippon Steel on Wednesday reported a 14.7% drop in April-December net profit to 440.9 billion yen ($2.98 billion) as improved margins and lower costs were offset by the absence of hefty inventory valuation gains booked a year earlier.

However, the company raised its full-year profit forecast through end-March to 470 billion yen from 420 billion yen, and its annual dividend forecast by 10 yen from its November estimate to 160 yen per share.

($1 = 147.9200 yen) (Reporting by Yuka Obayashi and Katya Golubkova; Editing by Stephen Coates and Mark Potter)