Ex-Portuguese Coach Carlos Queiroz, Iran in Cristiano Ronaldo's crosshairs as Portugal target last 16 in World Cup 2018

Cristiano Ronaldo will look to fire his country into the last 16 of the World Cup on Monday at the expense of former Portugal coach Carlos Queiroz and Iran.

Ronaldo and Queiroz are both appearing at their fourth World Cup, as player and coach respectively, and their relationship dates back to the Portugal captain's arrival as a teenager at Manchester United in 2003.

The 65-year-old served as Alex Ferguson's assistant over two spells either side of a brief stint in charge of Real Madrid, the club Ronaldo joined in 2009 in a deal Queiroz helped facilitate.

But their relationship soured following a second-round exit to Spain at the 2010 World Cup, after which Ronaldo suggested Queiroz was to blame for the defeat.

Portugal then crashed out in the group stage four years ago in Brazil, but Ronaldo is single-handedly leading their quest in Russia with all four of his team's goals so far.

"Our expectation is to continue our work and try to improve in the group phase. We're almost there (knockout stages) and then we'll see,” Ronaldo said after his early strike over Morocco left Portugal level on four points with Spain at the top of Group B.

Ronaldo is level with Belgium striker Romelu Lukaku in the race for the golden boot, leaving eternal rival Lionel Messi in the dust as Argentina scrap to stay in the competition.

Portugal coach Fernando Santos compared his talisman to a bottle of "Port wine", marvelling at the 33-year-old's ability to refine his game with age. Atletico Madrid Coach Diego Simeone, the former Argentina midfielder, even indicated he would prefer to have Ronaldo rather than Messi in his team.

"Messi is very good, but it is clear that he is very good because he is surrounded by extraordinary players (at Barcelona)," Simeone said, in an audio recording published by Spanish media outlets.

"The question I ask is if you have to choose between Messi and Ronaldo in a normal team, who would you choose?" Portugal defender Pepe, a long-time team-mate of Ronaldo's at Real, said it was a "privilege" for the country to have a player such as the five-time Ballon d'Or winner.

"He is getting better every year," Manchester City winger Bernardo Silva opined after Ronaldo's hat-trick in an opening 3-3 draw with Spain.

"People were waiting for him to get old and play worse, but he is only improving." Ronaldo scored a late penalty to seal a 2-0 win over Iran when the two sides last met, at the 2006 World Cup, and Portugal will hope for further inspiration from the second highest goal scorer in international history.

The European champions could be without midfielder Joao Moutinho after he sat out training again Saturday due to illness, although left-back Raphael Guerreiro is expected to shake off a leg problem.

Portugal need a draw to be sure of a place in the knockout phase, with either hosts Russia or Uruguay awaiting them in the next round should they advance.

"We have the level to do well. We believe in what we're doing and we've had a pretty good start to this competition, but there is room for improvement," added centre-back Jose Fonte.

Iran, who beat Morocco 1-0 before falling to Spain by the same score line, must beat Portugal to reach the latter stages of the World Cup for the first time.

Queiroz, who also took South Africa to the 2002 finals, called it "the most interesting and important match in my seven years with Iran".

"We will keep on working for our dreams, and our dream is to try and qualify for the second round. We know it will be difficult, but as I said before we came here and didn't expect easy things. Against Portugal, it will be match point for us,"he said after Wednesday's loss to Spain.