Washington, Mar 25 (IANS): A federal judge in San Francisco gave Volkswagen an additional month -- till April 21 -- to come up with a solution for around 600,000 diesel vehicles sold in the US that were fitted with software to hide their real level of toxic emissions.

US District Judge Charles Breyer had earlier given VW till March 24 to present its solution for those 2.0-liter and 3.0-liter diesel automobiles, Xinhua reported.

In a hearing on Thursday in San Francisco, the German automaker and the US Justice Department told Breyer that intense negotiations were ongoing but that more time was needed, according to the media.

The judge agreed to extend his earlier deadline after acknowledging the progress made thus far.

If VW does not provide Breyer with a solution by April 21, he could move to hold a trial in his court on the matter in mid-2016.

In January, the US Justice Department sued Volkswagen for up to $46 billion over the rogue software installed on diesel vehicles sold in the US since 2008.

That software -- known as a defeat device -- detected when emissions testing was taking place and activated the cars' emissions controls.

When those same vehicles were being driven under normal conditions, the controls were turned off and they spewed up to 40 times the US' legally allowable amount of nitrogen oxides, which have been linked to lung and respiratory illnesses.