Portsmouth manager Tony Adams says he will resign from his post if the club sell striker Jermain Defoe in January.

Tony Adams has told the club's owner Alexandre Gaydamak he will quit as manager if the club sell striker England Jermain Defoe - or any of the other players he wants to keep - in the January transfer window.

Defoe spurned a hat-trick of chances to bury wobbling West Ham in a goalless draw at Upton Park on Saturday.

Adams, who took over from Harry Redknapp three weeks ago, castigated former Hammers front-man Defoe for "maybe trying too hard" but also insisted: "He is going to help me stay in this job by scoring goals."

Adams added: "He's a threat (in front of goal) and I'm sure there will be some big clubs trying to get him but hands off because he's mine.

"Big offers? I can't wait .... because the owner has been very supportive and although I've not made an issue of it I've told him that everyone stays who I want to stay or I don't do the job.

"I told him that at the very start. He was very supportive of Harry and now he's being very supportive of me.

"He phones me on the way home and says 'what do you want, Tony, how can I help you and I say keep Defoe where he is and there's no problem. He says fine, anything else?' He's totally behind me."

Reports in September that would either sell Portsmouth or offload star players to ease the club's crippling debts were seen as a prime reason why Redknapp jumped at Tottenham's plea to drag them out of the Premier League basement where sacked Spaniard Juande Ramos had left them.

But ex-Arsenal and England ace Adams, who had been number two to Redknapp since July 2006 and claims he has his eye on one or two signings in the next window, clearly has huge faith in his employer's continuing loyalty to the cause.

Gianfranco Zola, another distinguished ex-player who has been a Premier League manager only six weeks longer than Adams, could clearly do with the same kind of reassurance, given West Ham's much-publicised parlous financial position.

Before Zola arrived to replace Alan Curbishley, the Hammers had to sell key players like Anton Ferdinand and George McCartney to try to balance the books after the revelation of their Icelandic owner Bjorgolfur Gudmundsson's staggering credit-crunch losses.

And it is obvious the Italian's immediate priority is top-flight survival this season.

He started well with two consecutive league wins back in September, taking Hammers up to fifth in the table, but they have been in freefall since then, gathering just one point from the matches before Saturday's stalemate.

Zola, who could charm the birds off the trees as a player at Chelsea, has now taken on a dour exterior as a coach and made no bones about being desperately grateful for a fortunate point against Portsmouth, especially as it came with the team's first clean sheet in 27 matches.

The shut-out was achieved through a combination of goalkeeper Robert Green's outstanding performance in defying the predatory Defoe three times in one-on-one confrontations and the Pompey front-man's over anxiety to stifle the jeers of the home fans who still abuse him for demanding to leave his local club West Ham as soon as they were relegated five years ago.

Zola said: "Robert played like a national team goalkeeper, not only with the saves but also because he looked so secure whenever he came out for the ball.

"It will be a big boost to his confidence and if he keeps playing like this I'm hopeful he will get the England call."

Not at the moment, though. Once again Green has been passed over for the friendly in Germany next Wednesday by England boss Fabio Capello who was at Upton Park on Saturday and looks set to stick with Pompey veteran David James who had little to do in the game.

And Zola, who coached Italy's under-21 team before joining West Ham, admitted his senior compatriot has never called him to recommend players for international selection in England.

Zola said: "This is all about Capello's considerations and not for me to choose but if you want to step up to international level you have to play at the top of your game consistently and we hope Rob Green will do that now."