One man is fighting for life and another has suffered serious injuries after a suspicious fire at an Irish pub in Sydney's west this morning.

Police were called to O'Donoghue's Irish Pub on the Great Western Highway at Emu Plains at about 1.45am.

Officers found a 29-year-old man on the road with serious burns and rendered assistance.

He was initially taken to Nepean Hospital before being transferred to Royal North Shore Hospital with life-threatening injuries.

Paramedics found another man on nearby Avoca Street who was also suffering serious burns.

He was taken to Concord Hospital for treatment.

Police said they have established a crime scene and are treating the fire as suspicious.

The Great Western Highway remains closed between Old Bathurst Road and Billington Place.

Commuter parking at Billington Place and Station Street has also been blocked while businesses at Station Street Shops will remain closed.