HSBC's high-profile Chairman Mark Tucker will exit the bank to take on a new role as chairman of AIA Group, the pan-Asian insurance firm where he once served as CEO, the companies said on Friday.

HSBC said Brendan Nelson, a former KPMG partner and board member who is the chair of the bank's group audit committee, would become interim chairman from Oct 1.

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The bank had announced on May 1 that Tucker would step down before the end of the year, but Friday's statement said he would depart on Sept 30.

Tucker, who was Hong Kong-headquartered AIA's chief executive and president from 2010 to 2017 before taking the HSBC role in September 2017, will replace Edmund Tse Sze-wing  as the insurer's chairman.

Tucker oversaw a major overhaul at London-based HSBC, during which the bank scaled back operations in Western markets such as the United States, Canada, and France, as part of a broader strategic pivot toward Asia.

Tucker was nearing the end of the nine-year maximum advised for chair roles under Britain's corporate governance code.

HSBC's senior independent director Ann Godbehere said the selection process to appoint a permanent chairman was underway. Tucker will serve as a strategic adviser to HSBC CEO Georges Elhedery and the board while the recruitment search remains in place.

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"Brendan's extensive experience on UK-listed boards, and as Group Audit Chair, makes him ideally placed to assume the role on an interim basis while the process continues," Godbehere said of Nelson.

He previously served as an independent non-executive director at several major UK-listed companies, including oil giant BP and financial services firm NatWest.

HSBC is expected to search for Tucker's successor from its current board, sources familiar with the bank's plans told Reuters. Among the leading candidates is former Citigroup President Jamie Forese, the sources said.