Having gone down 2-1 in an exciting tussle with defending champions Italy on Monday, David Platt's men need to raise their game and beat the Portuguese in Zurich tonight.
In their previous games, Portugal drew with Italy and in a surprise result, lost 2-0 to hosts Switzerland.
David Platt said: "We didn't want to have to use the safety net of needing a win against Portugal in the last game, but we are confident we can make progress."
Group A leaders Italy play Switzerland in their final qualifier tonight. Both games kick off at 7.30 pm.
Yesterday, France maintained their unbeaten record to top Group B as they defeated Belgium 2-0.
They are joined in the semi-finals by the Czech Republic who secured a point in a 1-1 draw with Greece.