By Lisa Barrington, Sophie Yu, Dan Catchpole and Tim Hepher

April 17 (Reuters) - Boeing BA.N faced new questions over the impact of tariffs on exports to China on Thursday as the spotlight fell on the fate of jets waiting at an aircraft completion plant near Shanghai.

The U.S. planemaker was reported earlier this week to face a Chinese ban on its imports, part of an escalating confrontation over U.S. Donald Trump's "reciprocal" global tariffs, though industry sources said the status of rules remained unclear.

In a sign that Boeing was preparing for normal business just weeks before Trump announced tariffs on April 2, tracking data showed four new 737 MAX planes sitting at a completion and delivery centre in Zhoushan, where Boeing installs interiors and paints liveries before handing aircraft to customers in China.

Three arrived in March and one arrived last week from Boeing in Seattle, according to Flightradar24.

However, aviation publication The Air Current on Thursday reported that the first of three of those planes had been tagged to be recalled to the United States without a handover.

Boeing declined to comment.

The planemaker opened the plant southeast of Shanghai in 2018 under the shadow of a previous round of trade tensions between Washington and Beijing during Trump's first presidency.

Although Boeing has not followed Airbus AIR.PA in assembling full airplanes in China, analysts said the aim was to build a lead in one of the world's largest air travel markets.

Airline and aerospace industry sources said there was no confirmation of a formal ban on Boeing deliveries, reported earlier this week by Bloomberg News, but that the imposition of tariffs would effectively block imports for the time being.

A senior industry source said Boeing and suppliers are planning on the basis that it would not be delivering planes to China for the time being.

China's foreign ministry declined to comment.

Asked by media about the reported ban, a spokesperson said: "I'd refer you to competent authorities".

DELIVERY LIMBO

For aerospace, Zhoushan is the latest staging post in a growing U.S.-led trade war. Planemakers, airlines and suppliers are reviewing contracts after Reuters reported that U.S. supplier Howmet Aerospace HWM.N had ignited a debate over the cost of tariffs by declaring a "force majeure event".

Confusion over changing tariffs could leave many aircraft deliveries in limbo, with some airline CEOs saying they would defer delivery of planes rather than pay duties.

Boeing historically sent a quarter of its deliveries to China but the proportion has been falling following earlier trade tensions, a 737 MAX safety crisis and the impact of the COVID-19 pandemic.

Analysts said a short-term halt in deliveries to China would not have an immediate major impact on Boeing, since it could serve other airlines and Airbus lacks spare capacity.

In the longer term, China remains a strategic market. Boeing says China will more than double its fleet by 2043, with the country set to overtake the U.S. in terms of air traffic.

Uncertainty over deliveries marks yet another setback for Boeing, which is navigating a slow recovery following a challenging year marked by a labour strike, enhanced regulatory scrutiny and persistent supply chain disruptions.

Boeing data shows 130 unfilled orders for China-based airlines and lessors, including 96 of its the 737 MAX. Industry sources say a significant portion of the more than 760 unfilled orders for which Boeing has yet to name a buyer are for China.

Chinese airlines lease 55% of their jets and it is "highly probable" they will try to extend any expiring leases for the time being, IBA Chief Economist Stuart Hatcher said.

(Reporting by Lisa Barrington, Sophie Yu, Dan Catchpole, Allison Lampert, Writing by Lisa Barrington and Tim Hepher; editing by David Evans)

((lisa.barrington@thomsonreuters.com;))