Pep Guardiola has urged his Manchester City players to be more clinical in the final third if they want to win the Champions League.

Glory in Europe's premier club competition has proved frustratingly elusive for big-spending City and the pressure on Guardiola to win the Champions League trophy is high.

The Premier League outfit have made a bright start to this year's competition, winning both Group C matches without conceding but, speaking ahead of a home fixture against Atalanta on Tuesday, Guardiola has acknowledged his side need to improve.

"I'm very confident – I have full trust in my team but there's a lot of strong teams [in the Champions League]," he told reporters.

"The Champions League will be won in the [penalty] box and so far we've not been very strong in the box.

"We've made mistakes we shouldn't make at this level, for example in the match against Watford, we created a lot of opportunities but scored very little. This is what I'm thinking.

"We're good at defending and we need to score at the right moment."

Guardiola repeatedly referred to City's profligacy throughout a pre-match news conference, adding: "In this competition, you have to be strong in the boxes and this season we're not incredibly strong in the boxes.

"Tomorrow we have the chance to improve. We need six more points to qualify."

Guardiola, who also mentioned his side will not have "20 chances" to win games in the Champions League, is expecting an entertaining match against Atalanta, the highest scorers in Serie A this season.

"It's a great joy to watch [Gian Piero] Gasperini's team play, they're brave...they take quite a few risks."

City defender Joao Cancelo was part of a makeshift back four on Saturday as Guardiola's team, playing without a recognised centre-back, won 2-0 at Crystal Palace.

The 25-year-old – an off-season arrival from Juventus – is aware of the threat that Atalanta can provide, even if they have failed to get a point in their two Group C fixtures.

"Atalanta are a strong team, a physical team and they press very well," he said.

"They have players that are technically skilled."

On City's new-look defence, Cancelo added: "It's true that in the last match we didn't have any central defenders but Rodri and Fernandinho are two extraordinary players."

Guardiola could choose to start John Stones against the Italian side, the centre-back featuring off the bench at Selhurst Park.

The manager also confirmed that defenders Nicolas Otamendi and Kyle Walker are on the comeback trail and that both trained on Sunday.