West Brom striker Kevin Phillips accused the officials of 'bottling it' after failing to penalise Milan Baros for handball in the FA Cup semi-final.
Portsmouth's Baros appeared to use his arm to control the ball before his shot was saved by Dean Kiely, Kanu tapping home the loose ball for the only goal at Wembley.
'You know what these officials are like, they tend to bottle it a little bit in these big games,' Phillips told BBC1. 'We can hold our heads up high, Portsmouth have been very lucky today if we found that goal when we dominated in the first half...'
Phillips continued: 'I'm gutted, I don't think we deserved to lose. We just couldn't find that goal but we've shown we are a quality footballing team.'
Portsmouth manager Harry Redknapp was delighted after seeing his side battle past West Brom into the final.
'It's fantastic to be going to a cup final,' Redknapp said. 'Full credit to West Brom, they made a game of it but it's a great day for the club. It's great for the support, I'm delighted for everybody.
'We didn't pass the ball as we can and they passed it better than us for long spells, they are a good team and I think they'll come up this year.'
Pompey goalkeeper David James added: 'I thought we dominated the game, they had a minimal amount of chances.
'It's typical of Portsmouth in the FA Cup this season, we seem to struggle first half but we were confident we were going to win the game.' West Brom boss Tony Mowbray said: 'No complaints - they are defensively a very well set up team and the experience they have at the back is invaluable to them. They are an exceptional team.
'We found it hard to break through today - the frustration is that we didn't threaten their goal enough today.
'It wasn't happening for us today. Our priority now is the league - we have six very important league fixtures to play and we will try to ply our trade in the Premier League next year.'