NSW water police vessel Nemesis is heading towards a stricken yacht carrying two people. (Jack Gramenz/AAP PHOTOS)

Rescuers are attempting to reach a yacht with two people on board in rough seas off the NSW south coast.

The Australian Maritime Safety Authority said it received a distress beacon alert about midday on Monday from a vessel 185km east of Nowra.

Media reports named the stricken 19-metre-long yacht as the Spirit of Mateship.

AMSA said it was dealing with up to five-metre seas and 70-90km/h winds.

Emergency authorities said a rescue was likely to be attempted at first light on Tuesday if weather conditions allowed.

A water police vessel was making its way to the scene.

Two Royal Australian Navy ships and an RAAF C-130J Hercules aircraft were also involved in the rescue operation.

Police had earlier said the yacht “is believed to have sustained a mechanical issue and is taking on water”.