The Hammers are still fighting on three fronts, the Irons flying high in fifth place in the Premier League table and through to the last 16 of the Europa League having finished top of their group.
West Ham have recently had a small number of coronavirus cases to contend with and the Hammers have key players either injured or absent but Moyes his signalled a strong warning about the capabilities of the team he will select in the FA Cup.
"I’d love to have a good run in the cup," said Moyes, as quoted by whufc.com.
"I want to do well in the Europa League as well, but also our league position last year gave us the chance in the Europa League, so you don’t want to give up your Premier League games very easily if you want to challenge the top teams.
“The balance of the whole thing is difficult to get right, but we’ll attempt to do that and try to put a really good team out against Leeds United.
“I think we’ve got a team that given the right draw, given the right moment, could easily go and challenge anybody for the FA Cup.
"Overall, we’ve got to get through the first tie, which we all know is a tough tie in the third round.”
West Ham will be without Saïd Benrahma who is on international with Algeria in the Africa Cup of Nations.
Defenders Kurt Zouma (thigh) and Angelo Ogbonna (knee) are long-term absentees whilst left-back Aaron Cresswell picked up a lower back injury in late December.
Pablo Fornals could return after a positive coronavirus test but Moyes said at his pre-match press conference that there had been a 'few' Covid cases within the Hammers squad and coaching staff this week.
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Thank you Laura Collins