PARIS, June 17 (Reuters) - Airbus was closing

in on an order for 100 single-aisle aircraft from VietJet

on Tuesday, with an announcement pencilled in for the

Paris Airshow barring a last-minute setback in negotiations,

industry sources said.

Airbus declined to comment and VietJet was not immediately

reachable at the air show, where airline staff were witnessed

preparing for a possible announcement.

The sources said the low-cost Vietnamese airline was looking

to buy the A321neo model. A deal for 100 such planes could be

worth around $6.3 billion, according to estimated prices

provided by analysts Cirium Ascend.

Bloomberg was first to report the potential deal.

European planemaker Airbus has announced a flurry of deals

at the Paris Airshow, the world's biggest aviation trade fair

that opened on Monday.

U.S. rival Boeing ( BA ) is expected to have a more subdued

show as it focuses on the probe into last week's fatal crash of

an Air India Boeing 787 and after it racked up huge deals during

U.S. President Donald Trump's recent tour of the Middle East.

VietJet, the largest airline in Vietnam, operates an

all-Airbus fleet, apart from two Chinese-made regional jets.

The airline has not to date taken delivery of any of the

around 200 MAX planes it has ordered from Boeing ( BA ).

Airbus is the main supplier of jets to Vietnam, with its

aircraft making up 86% of the planes currently operated by

Vietnamese airlines. However, export-dependent Vietnam is under

pressure from Washington to buy more U.S. goods.