Guardiola watched his team beat Espanyol 2-0 in the Catalan derby at the Nou Camp on Sunday night to move within a point of winning the title, just as Sir Alex Ferguson's side had done earlier in the day with a 2-1 victory at home to Chelsea.
Barca now look set to wrap up the Primera Division at Levante on Wednesday night, giving them more than two weeks to prepare for the showpiece at Wembley on May 28.
And Guardiola, who featured as a player in Barca's first European Cup success at the famous old stadium in 1992, admits he is wary of United's quality and strength in depth.
"They played a Champions League semi-final (second leg against Schalke) with a team full of reserves and they won 4-1 - that says everything you need to know about the quality they have," the Barca coach said.
"They have a great squad with two great teams and extraordinary players."
Nevertheless, the Barca coach is keen for his side to seal the league title before switching his thoughts to the Wembley date with the Red Devils.
"We will try to wrap up the league and then we'll think about the final," he said.
Xavi echoed the sentiments of his coach.
"We're almost there and we want to win it as soon as possible, so we can have our heads focused on Wembley," he said.
Meanwhile, Dani Alves hopes his side can build up positive energies ahead of the trip to London.
"We still need a point and I'm sure we'll get it," he said.
"The more charged we are with positive energy for Wembley, the better."
Captain Carles Puyol was deemed unfit to start against Espanyol, but Guardiola says he will be ready to play at Wembley.
"He was out for three months (recently) and the doctors decided he wasn't in shape to play today, but he is building up his fitness and will feature more in the next few games," he said.
Left-back Eric Abidal came on to play the last 20 minutes and Guardiola revealed the Frenchman, who has recently returned from an operation to remove a tumour from his liver in March, could also be ready to play in the Champions League final.
"Abi had a few minutes the other day (in the Champions League semi-final second leg against Madrid) and played for longer today," he said.
"We hope he can gradually play more and more and build up his fitness for the final."
But with the Wembley final in sight, Iniesta said: "We have a Champions League final ahead, so I don't think we will relax."
"We (Barca and United) know each other well - it will be a special final."
And team-mate Sergio Busquets added: "I'm confident we can win it, and bring some joy to our fans."
"The league is great, but it's not as prestigious as the Champions League."