If the Proteas win the upcoming three-match series, they will replace England at the summit of the International Cricket Council's standings.
South Africa captain Smith, speaking on the eve of the first Test, which starts at the Oval on Thursday, said his side's strong away record made them genuine contenders.
"We've been really consistent," said Smith on Wednesday.
"Maybe we haven't got some of the victories we would have liked but away from home our record speaks for itself. In all conditions I think it's fair to say that we've been the most consistent team over a period of time … We're looking forward to getting hold of that ranking and performing well. This Test series offers us an opportunity."
England captain Andrew Strauss acknowledged the home team faced "a very strong challenge".
He said: "South Africa are a very fine side. They've proved that over the last couple of years and they'll be determined to knock us off our perch … It will be a good gauge for us. The rankings say we are No. 1 and we have to go out and prove it."
'Topic of discussion'
Smith insisted he believed South Africa were well prepared despite only playing one two-day game and a three-day match before the Test series, both of which were rain-affected.
"I know it's been a topic of discussion but I think there's a real feeling of contentment and clarity in the squad. We've had more preparation time than on most of our tours. We're at a point where we want to be."
Opening batsman Smith claimed the touring team's bowling was stronger than when South Africa won their last series in England in 2008 – the last time England lost a Test series on home soil.
"Since the last time we played in England Morné [Morkel] and Dale [Steyn] are further on in their development and their skills and they still have the same sort of pace which is great," Smith insisted.
He added the introduction of Vernon Philander as a third seamer and Imran Tahir as a leg-spinner had given an extra dimension to the attack.
Both Strauss and Smith said the controversy over Kevin Pietersen's England future, which rumbled on Wednesday when the South Africa-born batsman was omitted from the initial World Twenty20 squad, had had no bearing on either side's preparations.
"The conversations Kevin has been having have been between himself, his representatives and the board," said Strauss. "It hasn't been a distraction to us, it hasn't entered our thinking … Kevin as much as anyone is determined to do well in this series and I haven't seen any signs in his preparation that he is in any way distracted," Strauss added.
"The big series bring out the best in him and often when he has a point to prove he does it with the bat."
Meanwhile Smith said it was not an issue with the South African team.
"It's not something that plays a role in our discussion. The Kevin Pietersen discussion in our team has been purely on tactics, how we are going to play against him, as it's been with every other player in the England line-up."
This will be Smith's 100th Test but the 31-year-old said the match was more important than the milestone.
"I'm extremely proud, it's something that doesn't come easy, but there is a bigger thing at stake here and that's the next 15 days of cricket," he said. – AFP