ExxonMobil says its £140 million investment project at Mossmorran's Ethylene Plant is 'on schedule' to start in April next year.
The firm says the global coronavirus crisis has affected the resourcing and delivery of equipment and materials.
Movement of key personnel involved in the project has also been impacted by the Covid-19 pandemic.
A new elevated flare tip is going to be installed at the site.
It aims to reduce noise and vibration which can sometimes be related with the use of the elevated flare.
Manager of the Ethylene Plant at Mossmorran Jacob McAlister said: "We want to update our host communities that we are on schedule to begin our work in April.
"Our commitment is to the health and safety of our employees, contractors and host communities and, therefore, our processes comply with all laws and regulations.
"This project is part of our long-standing plant investment cycle and there is no cost saving as a result of the adjusted project timeline."
Mr McAlister has also stated flaring will be needed to complete the installation of the new flare tip.
He added: "We know our communities are particularly interested in the new flare tip and have asked why this can’t be installed on its own.
"In order to properly complete the installation, flaring will occur prior to the work and upon re-start so we would want to do this only once alongside the other investment work – this is the right community and environmental decision.
"Furthermore, weighing in at almost 10 tonnes and fitted on a 100 metre tower, its installation requires a team of specialists and use of one of the country’s largest cranes, both of which are in high demand.
"We are working closely with regulators on this new schedule and we are committed to providing further updates to communities as our work on the project progresses."