Wilf
Slouching towards Billingham
I just saw this in a rather unmentionable source, so I won't link. I'd througt head to head games were the first stage tie breaker, but it's still good old goal difference apparently.
What each team needs to qualify
Tie breakers: If two or more teams are still level based on points, goal difference, goals scored and head-to-head results, then the fair play system will be used.
England
The Three Lions will qualify if they draw against Wales on Tuesday.
Southgate's side would move to five points with a draw, with Wales at best moving up to third on two points.
With Iran and USA - second and third respectively - facing each other, only one side can finish above England.
England, meanwhile, can lose to Wales and still progress. In fact, even with a 3-0 defeat to Wales they would still go through.
To guarantee first place in the group, however, they will need to beat Wales.
Iran
After their victory over Wales, Carlos Quieroz's side would seal qualification with a victory over the United States regardless of the other results in the group.
In fact, even if they were to only get a draw against the USA, they would go through if Wales failed to beat England.
However, if Iran draw with USA and Wales beat England, they will be out.
United States
Put simply, USA have to beat Iran to win; there is no other option.
With USA currently in third and behind Iran in second, a draw would leave them behind Tuesday's opponents.
Wales
Wales need to beat England in their final game to have any hope of making the next stage.
Even then it could still be difficult for them to advance. As stated, they need to beat England 4-0 in order to finish above the Three Lions.
Should they beat England by a lesser margin, they will finish below the Three Lions - and both USA and Iran would finish above them with a win of their own.
Essentially, Wales must win AND Iran vs USA must end as a draw... unless they beat England 4-0.