SEOUL/BEIJING (Reuters) - Chinese state-owned planemaker COMAC's first wide-body jet is in its "detailed design stage", an executive said on Tuesday, following a report from the jet's fuselage manufacturer aiming to deliver the first fuselage section by September 2027.

China, through the state-owned Commercial Aircraft Corporation of China (COMAC), has invested heavily in its attempt to break into a passenger jet market dominated by Western planemakers Boeing ( BA ) and Airbus.

COMAC has so far put the narrow-body C919 and regional jet ARJ21 into commercial operation, but its long-haul wide-body program has experienced delays. This included Russia in 2023 dropping out of a joint venture to develop the plane.

The C929 has entered the detailed design stage, COMAC marketing director Zhang Xiaoguang told a conference in Shangahi on Tuesday, local media reported.

In February Huarui Aero, the Chinese manufacturer selected by COMAC in 2021 to build the C929 fuselage, said the first "middle section of the fuselage" will be delivered in 2027, by Sept. 1.

This appears to be the first indication of a production timeline for the C929 since Russia left the project - formerly known as the CR929.

COMAC did not respond to a request for comment.

The C929 will have around 280-400 seats and a range of 12,000km, COMAC says.

Amid a global shortage of new aircraft, China has said it wants to advance COMAC's footprint domestically and internationally this year.

This includes a push for approval from Europe's air safety regulator for the C919, which is currently only certified by China.

Industry sources have generally welcomed COMAC's entry into the market, but caution that building competitive planes is a long project and have warned the landmark approvals from Western regulators could take years.

Only the ARJ21, of which COMAC has delivered 128, operates outside of China, with Indonesia's TransNusa.

COMAC's planes also rely heavily on Western-designed parts.

The C919 engines are supplied by CFM International, a joint venture between GE and Safran, but Aero Engine Corporation of China (AECC) is developing a domestic substitute that has not yet been certified.

China is also working on a domestic wide-body engine.

A COMAC representative at the Singapore Airshow last month said the C929's engine had not yet been chosen.