After taking a sensational early lead through Lee Bowyer, Geordie-boy Steve Stone levelled it up with a first-half deflection in a game that saw woeful United manage just two shots on target.
Shola Ameobi was given a chance up front alongside Craig Bellamy after Patrick Kluivert joined Alan Shearer on the injured list, while Ronnie Johnsen was left out as was Laurent Robert, who was named on the bench.
United got off to a dream start with a stunning Lee Bowyer goal inside three minutes, his first in the Premiership this season.
United old boy Lomana LuaLua was looking for a foul on the halfway line when he tangled with Bowyer only to see Steven Taylor seize possession and storm forward.
Bowyer responded immediately and charged forward to join Taylor and when the ball was played into his path the midfielder drilled and unstoppable shot beyond Jamie Ashdown and into the top corner.
It was not until the quarter hour mark that Pompey launched their first attack and won a corner that almost added to their woes.
The corner was cleared to the halfway line where another United old boy, Andy Griffin, was caught dwelling on the ball and robbed by the lively Bellamy.
The little striker raced forward before unselfishly picking out Kieron Dyer whose lung-bursting 80-yard run ended with him lifting his left footed attempt over the bar from just eight yards out.
There was an amazing let-off for Ashdown after 27 minutes when the keeper decided to change feet to clear a Griffin back pass only to slip and could only watch helpless as the ball crept narrowly past the post for a corner.
Seconds later Steve Stone was cautioned for dissent and Bowyer's free-kick flew across the face of the goal and just evaded the lunging Taylor at the back post.
But out of the blue, and as happened so often this season, Pompey drew level after 29 minutes through Gateshead-born Stone.
After Bowyer had cleared an Ricardo Fuller header off the line the ball was eventually pulled back to the former England midfield man whose 20-yarder struck Jenas and wrong-footed Shay Given who had the ball covered on the way to his right.
United hit back and almost went back in front courtesy of their youngest duo on the park. Taylor crossed deep from the right and Jonathan Milner's left-foot volley flew into the sidenetting.
This was just so typical of Newcastle, some outstanding football but unable to finish off their opponents, a feature of the season.
United sent on Robert for Milner just before the hour mark and the enigmatic
Frenchman immediately brought a save out of Ashdown in what proved to be the second and final United effort on target.
Stone was fortunate not to see red after 67 minutes after taking Dyer out in full flight. Stone had already been booked and had got away with another bad challenge in the first half against Jenas.
Jenas and Bowyer continued to fire in midfield and it was somewhat surprising when the latter was replaced after 71 minutes by Darren Ambrose.
Skipper Jenas worked tirelessly in his effort to restore Newcastle's advantage as Pompey were constantly pinned back in their own half.
Fuller should have done better when too easily slipping Titus Bramble, but was then let down by his finishing.
Poor finishing was again to blame after 81 minutes as Pompey could easily have returned to the South Coast with all three points.
LuaLua found Stone on the right to whip over a perfect cross for Gary O'Neil, who from just six yards planted his header wide of the target when he should have scored.
Dyer, who worked extremely hard, fired over from 20 yards and in the final seconds Ameobi started a move that he finished but only managed to toe poke wide.
Pompey's blatant time-wasting resulted in five extra minutes but Newcastle remained unconvincing and the jeers from the home fans told their own story.
Man of the Match: Jermaine Jenas - The young Magpies skipper worked tirelessly and covered ever blade of grass on St James' Park for the Newcastle cause.