Shannon Albuery was on target as Pompey Women were forced to share the points with Oxford at Westleigh Park.
The striker found the target in the first half to cancel out an opening effort from United’s Carly Johns.
Jay Sadler made three changes from the side that were narrowly beaten at Crawley earlier in the week.
Rebekah Tonks, Dani Lane and Albuery all returned to the starting line-up, with Jazz Younger, Ava Rowbotham and Emma Jones making way.
The visitors took an early lead when a Kayleigh Hines free-kick came back off the post and Johns was first to the loose ball.
Pompey looked to hit back immediately and Rose Kite was called into action to keep out Albuery’s angled attempt.
The United keeper then did well to claim a dangerous delivery from Evie Gane and prevent Hayley Bridge from making a connection.
But the leveller did arrive on 35 minutes after a spell of intense pressure forced a mistake in the visitors’ defence.
Cherelle Khassal drove forward with the ball and found Jade Bradley, who in turn played in ALBUERY to curl a shot into the corner.
Half Time: Pompey 1 Oxford 1
Albuery set about trying to find another following the restart, but could not quite latch onto a threaded Sammy Quayle pass.
And when she did get a shot away from the edge of the box, it was tipped over the bar by the impressive Kite.
Sadler made changes to add some fresh impetus to his side, with Rosie McDonnell, Rowbotham and Jones all entering the fray.
Albuery continued to torment the Oxford defence as the seconds ticked down and headed a Bradley cross into the side netting.
She then turned provider to create an opening for Lane, but she could only fire straight into the arms of Kite.
And it was the keeper who had the final say deep into stoppage-time to keep out a curling effort from Jones and ensure the spoils would be shared.
Pompey: Haughton; Tonks (Rowbotham 74), Gotch, Gane; Rowe; Bridge, Lane, Bradley (c), Quayle (McDonnell 63); Khassal (E.Jones 74), Albeury
Subs not used: Younger, F.Jones