Lassana Diarra scored his first Portsmouth goal and Niko Kranjcar added the winner but Harry Redknapp's team had to come from behind to survive a fierce FA Cup challenge by Coca-Cola Championship visitors Plymouth Argyle.

Chris Clark opened the scoring in the first five minutes to put the hosts on the back foot and a replay could have been in store had Sylvain Distin conceded a penalty in the closing stages.

Argyle's travelling fans appealed for the decision when Distin, captaining the Pompey side, appeared to handle in the area 11 minutes from time. But he was relieved to see a only a corner awarded.

And Peter Halmosi, by far the game's outstanding player, shot agonizingly wide just before the end of a thrilling game in which David James was by far the busier of the two keepers.

The Pilgrims, quarter-finalists last season, were well up for the cup despite just one win in the previous seven games - an estimated 3,000 of their fans making the trek along the south coast and filling one end of Fratton Park.

And although Pompey soon showed their passing skills to put a fractionally offside Benjani Mwaruwari in on goal in the opening minute, it was Argyle who took a shock lead with just four minutes on the clock - and Clark claiming a debut goal.

The former Aberdeen player was left in acres of space on the right side of the Portsmouth penalty area and the ball fell at his feet after Distin made a block tackle on the edge of the area to thwart an advancing David Norris.

Clark's shot took a big deflection off Hermann Hreidarsson, who should have been marking him, and spiralled over James.

Pompey were clearly stunned and James had to make a string of fine saves as Argyle tried to push home their advantage.

The keeper stretched low to keep out successive shots from Rory Fallon, Halmosi and Jermaine Easter after the trio all tried their luck against a home defence lacking injured Sol Campbell's considerable influence for a second successive week.

Norris and Easter made James work hard yet again and although Pompey gradually imposed their superior technique, it was not until the 33rd minute when Diarra's first goal for the club broke Argyle's defensive screen.

Luckless striker David Nugent, who was taken off at half time, was slow to react to an opportunity after 20 minutes when Glen Johnson crossed and was frustrated again when his snap-shot was deflected over the bar 13 minutes later.

But the corner was played short by Kranjcar and Pedro Mendes, finally reaching Diarra 25 yards out and he buried an emphatic low drive via a slight deflection.

Johnson, slack in defence, set up a chance for the persistent Easter to jab against a post with James rooted to the spot.

But almost immediately Johnson made amends with a fine cross at the other end and although Kranjcar failed to reach it with a leaping header, it came back to him off Norris and he coolly slotted it in.

Yet Argyle simply refused to give up the fight in the second half and successive shots by Halmosi and Easter gave James further trouble.

Pompey, left without a replacement striker when Nugent could not continue with a groin injury, often had to pull everyone back behind the ball to protect their lead, although Benjani, now a lone striker, worked hard to manufacture a couple of chances which he fired just off target.

And Pompey had a major escape in the 79th minute when Distin appeared to handle the ball as he challenged Fallon for a left-wing cross.

Pilgrims fans chanted their derison at the official and Pompey boss Redknapp stood anxiously gnawing his nails on the touchline right to the end.

Teams:

Portsmouth James, Johnson, Pamarot, Distin, Hreidarsson, Lauren (Davis 67), Pedro Mendes (Hughes 90), Diarra, Kranjcar, Nugent (Mvuemba 46), Mwaruwari.

Subs Not Used: Begovic, Aubey.

Booked: Pamarot.

Goals: Diarra 34, Kranjcar 45.

Plymouth McCormick, Connolly, Timar, Doumbe, Sawyer, Clark (Folly 82), Nalis, Norris, Halmosi, Fallon, Easter (Jutkiewicz 75).

Subs Not Used: Larrieu, Hodges, Summerfield.

Booked: Halmosi, Doumbe.

Goals: Clark 5.

Att: 19,612

Ref: Andre Marriner (W Midlands).