HANOI, Jan. 11 (Reuters) - The head of Vietnam's Communist Party Nguyen Phu Trong is expected to miss on Friday the second state visit of a foreign leader to Hanoi in less than a week amid concerns about his health.

Trong, 79, who has been at the helm of the party since 2011, is the most powerful leader in Vietnam's one-party political system and regularly receives visiting foreign dignitaries in private meetings.

But he is not scheduled to meet Indonesia's President Joko Widodo during a state visit on Friday, according to draft agendas from Vietnam's foreign ministry and Indonesia's presidential office.

Trong was also not on the list of Vietnamese leaders who received Laos' Prime Minister Sonexay Siphandone last weekend.

He has not been seen in public since Dec. 26, when he met in Hanoi the head of the Japanese Communist party Kazuo Shii.

Vietnam's foreign ministry did not immediately reply to a request for comment about Trong's health.

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