Vehicular emissions are among the main causes of air pollution.
The National Green Tribunal (NGT) on Wednesday is set to hear the diesel vehicle ban case.
The tribunal had on July 18 asked the Delhi's transport authorities to cancel registration of diesel-fuelled vehicles that were older than 10 years.
Two days later, it asked the Delhi Government to first focus on vehicles order than 15 years.
The centre was expected to oppose the tribunal's order to phase out more than 15 years old diesel vehicles in Delhi.
The Union Government had on July 29 challenged the NGT's order to phase out diesel vehicles, saying there was no legal provision for the move described by a carmaker as a "corporate death penalty".
The Supreme Court has also stopped registration of new diesel vehicles with engine capacity of 2000CC and above and ordered all diesel taxis to convert to compressed natural gas.
Vehicular emissions are among the main causes of air pollution and diesel one of the biggest contributors.