Anson: 2018 race still wide open
But bid chief executive Andy Anson was also bracing for the airing of a British TV documentary on Monday night about alleged corruption in FIFA, saying England's chances would inevitably be affected by the fall-out.
FIFA's executive committee - currently reduced to 22 members after two were suspended earlier this month - will decide on Thursday the hosts of the 2018 and 2022 World Cups.
Anson said he knew how many votes England had guaranteed for 2018 although he would not reveal the number.
"We're optimistic," he said. "We know we have a lot of work to do this week."
"I know who's committed to supporting us and I know the votes we can get," he added.
"We have to work very hard over the next three days to make sure it comes to fruition. We may be underdogs but we can win it."
England are up against Russia, Spain/Portugal and outsiders Belgium/Netherlands. "We've got three strong contenders and any of them can still win on Thursday. They're all good bids," said Anson.
He then returned to the subject of the BBC Panorama programme, due to be aired on three days before the vote.
"Of course I'm disappointed with the timing and it's certainly not going to win any votes," Anson told reporters.
"We just have to see what happens tonight and move on. I won't be watching it, I've got other things to do."
He added: "It's a reality, it's a small group of 22 people, in a way it's a brotherhood of executive committee members. If you hurt one of them, of course it has an impact on the others. That's just inevitable.
"I think we have to be aware of the implications and act accordingly. We'd be naive if we didn't think these things had an impact."
Two executive committee members - Reynald Temarii and Amos Adamu - will miss the vote after being suspended following an investigation by the Sunday Times saying they offered to sell their votes for cash.
FIFA are still to decide on a request from the Oceania Football Confederation to replace Tahiti's Temarii for Thursday's vote.
The fall-out from the Sunday Times reporters and Monday's BBC documentary is regarded as the most serious threat to England's campaign.
Anson felt the decision to choose the 2018 and 2022 hosts together had given the contests a much more political edge, especially as eight members of the FIFA executive committee were from bidding nations.
He said: "Obviously, the strength of the bid is important but when you've got 22 people with two campaigns, who've got their own issues or agendas, or their own elections to worry about, of course politics are involved.