Newport 3 Pompey 0
Pompey limped out of the Johnstone’s Paint Trophy with a disappointing display in south Wales.
Conor Washington took advantage of some generous defending to open the scoring before Deji Oshilaja headed home a second.
David Pipe’s second half red card gave the travelling Blues fans hope, but that was extinguished when Washington grabbed his second of the evening late on.
Guy Whittingham made five changes from the side that exited the FA Cup at Stevenage on Saturday.
Tom Craddock made his first start since August up front, while Danny East came in at left-back and Ricky Holmes, Romain Padovani and Shaun Cooper returned to the midfield.
Jed Wallace and Gavin Mahon were both suspended, while Simon Ferry (hamstring), Thery Racon (hip) and Patrick Agyemang (thigh) also missed out.
Pompey won a number of set-pieces in the opening stages, but were unable to test County keeper Jamie Stephens.
Instead it was the hosts who broke the deadlock on five minutes thanks to a disastrous mix-up in the Blues back-line.
Trevor Carson raced from his goal to collect a long ball, but Bondz N’Gala had not noticed and his header was latched onto by Washington, who was left with a simple finish.
Padovani tried to bring Pompey level, but his arrowed effort from 35 yards was always clearing the crossbar.
But the visitors were looking shaky at the back and Washington burst past Joe Devera before whipping in a dangerous cross that Carson did well to hold.
And they doubled their advantage on 18 minutes after Padovani had been booked for a clumsy challenge on Christian Jolley.
Carson did well to get a hand to Robbie Willmott’s swerving free-kick, but Oshilaja was well placed to head home the loose ball.
Pompey, meanwhile, were struggling to find any fluidity going forward, giving away possession far too easily.
Newport were still looking to expose any weaknesses at the back and a corner caused an almighty scramble in the Blues box before Carson was eventually able to grab hold of the ball.
The visitors did at least have a chance on 36 minutes, with Padovani diverting Holmes’ cross narrowly over the bar.
A neat passing move then ended with Stephens having to get down quickly to keep out Holmes’ drive.
The Blues were suddenly looking a lot brighter and Cooper saw his skidding effort palmed around the post by Stephens.
But they were unable to make a dent in Newport’s lead and went in two goals down at the interval.
Half Time: Newport 2 Pompey 0
Whittingham resisted the urge to make changes at the break, but David Connolly replaced Craddock nine minutes into the second half.
But it was Bird who went close to scoring soon after, glancing a header wide after meeting Cooper’s cross.
Padovani then attempted an audacious volley from distance, only to be denied by an alert Stephens.
But Newport were still looking dangerous themselves and Ismail Yakubu sent a header inches past the post.
They had to play the closing stages with 10 men, however, after Pipe was sent off on 67 minutes.
The Newport skipper made a two-footed lunge on Holmes as he burst forward down the left and referee Graham Scott quickly pulled out a red card.
County were still looking comfortable, though, and Carson did well to deny Washington after the forward burst through on goal.
A couple of set-pieces did cause some concern, but the ball would not fall kindly for the Blues inside the box.
And the hosts made certain of their place in the area semi-finals on 82 minutes when Washington out-muscled Devera and slotted the ball home.
The visitors were even denied a consolation late on when Sonny Bradley netted, only for Scott to spot a handball in the build-up.
Newport (3-4-3): Stephens; Yakubu, Oshilaja, Worley; Pipe (c), Naylor, Flynn (Minshull 60), Willmott; Jolley (Jackson 71), Crow, Washington
Goals: Washington 5, 82, Oshilaja 18
Sent off: Pipe
Booked: Flynn, Crow, Jackson
Subs not used: Pidgeley, James, Jones
Pompey (4-4-2): Carson; Devera (c), N’Gala, Bradley, East; Holmes, Cooper, Padovani, Barcham; Bird, Craddock (Connolly 54)
Booked: Padovani, Bradley
Subs not used: Smith, Painter, Ertl, Marquis
Referee: Graham Scott
Attendance: 2,849 (619 Pompey fans)