Dominic Heaume scored one of St Martin's two goals against Bels
Northerners look favourites to win Guernsey's Senior County League Division One title after champions Belgrave Wanderers lost on Saturday.
Bels went down 2-0 at third-placed St Martin's thanks to set-piece headers from Billy Page and Dominic Heaume.
That meant North went three points clear of Wanderers after they recorded a 3-1 win over bottom side Rovers.
North, having trailed Bels most of the season, need only a draw with Bels in Tuesday's showdown to take the title.
Hopefully if we get on top on Tuesday and score goals we'll have a chance of getting something out of it. We're going to go all out and give it everything
Bels manager Micky Ogier
A Bels victory over North at the Track would force a play-off.
"We just haven't had that little bit of luck lately," Bels manager Micky Ogier told BBC Guernsey.
"Up front, the ball's just not running for us. But hopefully if we get on top on Tuesday and score goals we'll have a chance of getting something out of it.
"We're going to go all out and give it everything."
The defeat was Bels' third of the season and means they have failed to beat St Martin's in all three of their fixtures this term, having drawn the previous two encounters 2-2.
"We were very relaxed - we're very competitive at the moment and we're playing very, very well," St Martin's boss Colin Fallaize said.
"Because we've got players playing for places in the semi-final of the FA Cup and the final of the Jeremie Cup, our situation is one which is very relaxed but ultra-competitive and that caused a bit of a problem for Bels."
In the day's other match, Vale Rec leapfrogged Sylvans to go third from bottom after beating them 2-1 at St Peter.
This page is best viewed in an up-to-date web browser with style sheets (CSS) enabled. While you will be able to view the content of this page in your current browser, you will not be able to get the full visual experience. Please consider upgrading your browser software or enabling style sheets (CSS) if you are able to do so.