Arias struck in the 14th minute, guiding home a cross from substitute Luis Suarez, and Colombia's disciplined defence did the rest as Nestor Lorenzo's side extended its unbeaten run and booked a meeting with Switzerland in the next round.

Colombia had largely flown under the radar at the tournament, despite going undefeated against Portugal, Uzbekistan and DR Congo to top Group K.

Its breakthrough on Saturday (AEST) came from two players who had not been expected to combine, as Suarez, thrust into action after Jhon Cordoba was forced off with an apparent groin injury in the eighth minute, delivered a pinpoint cross to the back post where Arias had somehow drifted unmarked.

With time and space to pick his spot, Arias calmly guided the ball into the bottom corner to hand his side a deserved lead.

The stadium felt more like Barranquilla than Kansas City as tens of thousands of Colombia supporters turned the clash with Ghana – a team ranked 60 places behind Colombia – into a de facto home game, giving the South American side a level of support rarely seen so far from home.

Luis Diaz had numerous scoring chances. He fired into the side netting in the first half, then celebrated what he thought was the game's second goal early in the second half when he slotted home Arias's cross, but it was disallowed for offside.

"We need to stay grounded, take it step by step, remain calm and keep improving," Diaz said. "That's what football – and life – is all about. So, I'm very relaxed, focused on working for what's ahead, and getting some rest, which is going to be extremely important."

Lorenzo's men continued to push for a second goal, and Ghana goalkeeper Lawrence Ati-Zigi, who was excellent all night, made one terrific save after another in the dying minutes as Colombia's fans cheered every one of their team's touches of the ball.

Antoine Semenyo was Ghana's biggest attacking threat, yet Colombia's disciplined defence denied him a clear sight of goal.

"They controlled much better the game," Ghana coach Carlos Queiroz said.

"The passing, the movements, and doing that, they damaged our fitness and our ability to recover the ball and try to go forward.

"We tried to go forward, tried to create opportunities, but for any reason, the last pass, the last service, was not with the quality that was necessary in this case. So, I think the best team won."

Los Cafeteros became the fourth South American team to reach the Round of 16, joining surprise package Paraguay, which stunned Germany, along with Brazil and Argentina, both of which survived scares of their own.

Colombia will play Switzerland on Wednesday (AEST) in Vancouver.