West Ham started the season by conceding six goals in successive defeats to Aston Villa and Bolton before scraping past Oxford in the Carling Cup. With their next four fixtures against United, Chelsea, Stoke away and Tottenham, West Ham could quite conceivably enter October without a single point to their name.

But Grant is convinced West Ham are ready to rise to the challenge.

"Manchester United will not have an easy life tomorrow night," he vowed.

"They are a good team and they have top players. Not only Wayne Rooney and Javier Hernandez but also Dimitar Berbatov and Paul Scholes, who I think becomes younger every year.

"At the moment they are the best players in England. Manchester United are a better team than West Ham - but I believe in football anything can happen.

"The better team does not always win. We need to do a few things to make their lives difficult.

"One thing I don't want is for us to give up before the game, nor in the game. I always say to my players to be positive.

"It is a big challenge. If you don't take a hard situation as a challenge you cannot succeed, not in sport, not in life."

West Ham will need to make a significant improvement even to make life difficult for Manchester United. They were thumped 3-0 by Aston Villa before losing 3-1 at home to Bolton.

But Grant believes West Ham lost despite being the better team against the Trotters - and that reinforces his point that Manchester United are not invincible.

Grant said: "I see the players in training every day and I'm confident we can do something.

"We didn't play well in the first game but in the second game we played good football. We deserved to win - but there is no 'deserve' in football.

"Manchester United are a good team, yes, but football is football."

Grant's confidence is also born from his experiences at Chelsea and Portsmouth, who were both in a state of turmoil when he arrived.

In 2007, Chelsea had just lost Jose Mourinho but Grant led the club to the Champions League final and to the brink of the Premier League title.

On both occasions they were beaten by Manchester United - on penalties in Moscow and on goal difference in the title race - but Grant is not after revenge.

"My father always told me not to live in the past," he said.

"The Champions League final is one of my proudest moments but on the night it was not easy.

"One thing that I like to do with my team is always to progress.

"In Chelsea I received a team in a situation and we progressed and in Portsmouth it was the same and in the last two or three months it was good.

"West Ham asked me to come here for four years. It is a very exciting project. We are only at the beginning."

West Ham yesterday signed 23-year-old Nigerian striker Victor Obinna on loan from Inter Milan with a view to a permanent deal next summer.