Lionel Messi missed a penalty in the shootout but Argentina still came out on top after a nervy encounter versus Ecuador to win 4-2 on penalties and reach the Copa America semi-finals.

Messi could not convert the defending champions' opening penalty, but Emiliano Martinez came to the rescue and saved Ecuador's first two efforts and then Nicolas Otamendi found the net to secure the 4-2 victory.

Normal time had ended 1-1, Kevin Rodriguez having equalised for Ecuador in the 91st minute and the underdogs still had to time to carve out a golden opportunity to snatch victory.

Ecuador enjoyed the best of the opening half hour, Jeremy Sarmiento forcing an early save from Martinez while Angelo Preciado clipped Enner Valencia's cross over the bar.

Gradually, Argentina started to assert some control and went ahead after 34 minutes as Messi's corner was flicked on and Lisandro Martinez was left unmarked to head in at the back post.

They missed a golden chance to double the lead before the break as Enzo Fernandez fired wide after Ecuador lost possession at the back.

But Ecuador again started the second half strongly, Enner Valencia sending Martinez the wrong way from the spot only to roll his effort against the post after Rodrigo De Paul was ruled to have handled a deflected corner.

Ecuador continued to press. but had to wait until stoppage time before equalising as Rodriguez glanced his header from John Yeboah's cross into the net — the goal standing after a lengthy VAR check for offside.

They could have clinched the win in the remaining time, Jordy Caicedo heading wide as he arrived late to meet a cross.

With no extra-time, the match headed to penalties and Messi's cheeky chip down the middle only found the top of the bar.

But Martinez came to his rescue, saving from Angel Mena and Alan Minda and there was no coming back for Ecuador.