Brown took time out from the Commonwealth summit in Trinidad and Tobago to meet CONCACAF president and FIFA executive member Jack Warner, who said last month that England's bid was falling off the pace.
Brown told Warner the government was completely committed to the success of the England bid and was ready to do whatever was necessary to support it, a British official said.
"It was an opportunity for the prime minister to re-emphasise how important this is to the country and how personally committed he is," the official said, describing the meeting as friendly and open.
Warner spoke of the quality of British infrastructure and stadiums, the official said. But there were other factors that influenced the decision on who was awarded the event, the official added.
England are among 10 bidders for 2018 but Warner said last month the country was failing to take full advantage of its attributes and the likes of Spain and Russia were making a strong early impression.
Football's world governing body FIFA will decide the 2018 host country in December 2010 and Warner's support would be important to England's chances of hosting the event for the first time since 1966.
Premier League chairman Dave Richards resigned from the board of England's 2018 World Cup bid this week, saying he could best support the campaign without sitting on the board. It followed the resignation of six members earlier this month.
