Blatter said: "The easiest way to organise the World Cup is to go to England. Everything is there - fans, stadiums, infrastructure."
But he added: "You cannot deny Russia if they bid for something. They are more than a country. They are a big continent, a big power."
The six-man Fifa team, led by the president of the Chilean football federation Harold Mayne-Nicholls, travelled from Downing Street to Wembley Stadium by tube where they inspected the facilities and met England manager Fabio Capello on the pitch.
On Tuesday morning, the inspectors are due to have several presentations followed by a boat journey along the River Thames.
The party will fly over a number of proposed 2018 venues including the new Olympic Stadium, Arsenal's Emirates Stadium, White Hart Lane, Stadium:MK in Milton Keynes, Nottingham Forest's City Ground and Elland Road in Leeds.
They are due to arrive in the north east for more presentations in the afternoon before visits to Sunderland and Newcastle.
On Wednesday, the focus moves to Manchester where Old Trafford and the City of Manchester Stadium will be in the spotlight. The visit concludes on Thursday.
Clegg, who was joined by Culture Secretary Jeremy Hunt and Sports Minister Hugh Robertson when he greeted the delegation at Number 10, believes Fifa will be won over by the size of the support for the English bid.
"The excitement and passion behind this bid is huge," said Clegg. "It will inspire people in towns and cities across the country.
"There are few nations that can claim the passion we in England have for football.
"Our job is to show you we already have the infrastructure and facilities to host a World Cup."
Fifa's inspection team, which also included South Africa's World Cup organising chief Danny Jordaan, were in England after previously travelling to Russia to witness their rival World Cup bid.
With trips to 2022 hopefuls Japan, South Korea and Australia completed, Fifa will spend a total of four days in England before moving on to look at the facilities of the joint Spain-Portugal bid and then the United States and Qatar in September.
Fifa bid inspection leader Mayne-Nicholls said: "We believe that only with the support of the governments can we keep taking the game to all of the places in the world.
"We will ask all the doubts we have, we have been studying the bids and we will work with the local organising committees before writing a very fair report to take back to Fifa headquarters.
"We will do our best to write an objective report."
England 2018 bid chief executive Andy Anson said: "Just like Fifa, we believe in the power of football to open up new territories.
"Our new territory extends beyond any national boundary and directly benefits every country - each of Fifa's 208 member associations.
England 2018 bid chief Anson bullish on host chances
"A tournament in England will deliver a global legacy that will produce greater football and social benefits for more people than ever before."
"We will show that a Fifa World Cup in England is not just about what it can do for England, but about what a Fifa World Cup in England can do for the rest of the world."
Anson also disclosed that Prime Minister David Cameron, currently on holiday in Cornwall, would be hosting a visit by Fifa president Sepp Blatter in the autumn.
He added: "All candidate host cities have a valuable part to play during this week and they have all been exceptionally supportive and co-operative during our planning.
"We believe our bid book reflects a strong proposal to Fifa from a country that can deliver on facilities, commercial opportunities and general infrastructure, for the overall benefit of the tournament, its players and officials and the fans.
"England's bid is based around stadiums and facilities that are already in place and already being used on a regular basis and so there is minimal construction and planning required."
Meanwhile, sports minister Mr Robertson told BBC Radio 5 live: "There is a fantastically exciting period in front of us.
"We really want to win this 2018 World Cup bid, it would be fantastic for football in this country.
"I think we have got a really good offer to take out to Fifa and we are all determined to do everything possible to bring this home.
Hunt insists bid team playing by rules
"The great thing about our bid is all the infrastructure is there, it's all ready. You could technically hold the World Cup here tomorrow."
England have a number of official ambassadors backing their campaign including England players David Beckham and Rio Ferdinand, 2008 Formula 1 world champion Lewis Hamilton, and musicians Noel Gallagher and Sting.
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