Silva nodded in the only goal from Cristiano Ronaldo's cross to keep the pressure on Group B leader Switzerland, which remains three points clear after beating Latvia.

The visitor's task was made easier by the first-half dismissal of former Watford and Ipswich forward Tamas Priskin, although Fernando Santos's side did have to wait until after the interval for Silva to break the deadlock.

Hungary defended stoutly either side of Priskin's elbow on Pepe but rarely threatened an upset, failing to register a shot on goal.

Ronaldo, fresh from a hat-trick in Friday's (AEST) 5-1 victory over Faroe Islands, was kept quiet at the other end and will have to wait for what would be a record-breaking 15th goal of this qualifying campaign.

With Bernd Storck's men now out of the running, Portugal only needs to beat Andorra next month to set up a showdown with Switzerland, which has an inferior goal difference, to determine who progresses straight to Russia.

Ronaldo began his goal-hunt as early as the fifth minute, stinging the palms of Peter Gulacsi from distance and then heading a far-post cross inches wide of the upright.

Hungary steadied after a concerning start and managed to restrict the visitors to a series of blocked attempts from outside the area, although Cedric Soares should have produced a better touch when a ricochet fell into his path.
 
Priskin, however, brought that good work undone when he was shown a straight red card on 30 minutes for catching Pepe in the face with a stray elbow.
 
Balazs Dzsudzsak scored twice when the two teams drew 3-3 at Euro 2016 and the skipper cleverly picked out Gergo Lovrencsics for Hungary's best chance of the half, but the Ferencvaros man failed to test Rui Patricio with a difficult shot on the turn.
 
Fabio Coentrao, back in Portugal's squad for the first time since October 2015, was withdrawn due to injury before that action and Santos' frustration grew on the stroke of half-time as Silva shot straight at Gulacsi following an intricate team move.

Silva only needed three minutes of the second half to redeem that missed chance, the 21-year-old nodding in Ronaldo's perfect dinked to the far post.

Portugal was content to take the sting out of the contest following Silva's goal and, after Gulacsi diffused one chance for a potential second, Santos' side comfortably saw out the remaining 15 minutes to set the stage for a blockbuster October.