Koeman wanted to take Liverpool midfielder Wijnaldum and Manchester City defender Garcia to the Nou Camp during the summer.
But cash-strapped Barca could not come up with the cash to tempt either club to sell.
Now Koeman wants the pair in January – and also continues to target Lyon's former Manchester United striker Memphis Depay.
All three players are out of contract next year and the Barcelona coach is hoping his club can raise enough money to seal a trio of deals.
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Koeman confirmed: “Our interest for Wijnaldum is strong.
“I wanted to bring him here in the summer because he has the ability to make fantastic runs from midfield and turn up in the box at the right moments.
“I am convinced he can really add something to the team. But the financial situation of Barcelona was known at his club.”
Koeman added: “There is a chance for sure that we are going to have another go for Garcia.
“But right now I cannot know how the finances of the club are in January, so I have to wait and see.”
United still have an option to buy back Depay, but Barca had a contract ready for the Dutchman to sign in the last transfer window.
Koeman said: “Everything was ready, but because of the La Liga rules we knew we had to sell first before we could sign our targets.
“In the end it was not possible. It was disappointing, but Memphis knew how the situation was at Barca.”
Depay has scored 58 goals in 144 appearances for Lyon since his £16million transfer from United in January 2017.