Head coach Peter Vermes has acknowledged that the club have been forced to focus their search for attacking reinforcements elsewhere for now.
Van der Vaart, 32, is out of contract with Hamburg in the summer and the Bundesliga side’s sporting director Dietmar Beiersdorfer revealed last week that he will not been offered an extension.
Sporting KC’s interest in the Dutch midfielder has been known for some time now and club CEO Robb Heineman confirmed last month that team officials have travelled to Europe to meet for talks over a potential MLS move.
Heineman even stressed at the time that finances weren’t an issue, telling MLSsoccer.com: “If we can get that done, we'd like to get it done. He'd be a July move – maybe earlier. I don't know if Hamburg would let him out early. There's a lot of things to work out with him.
“It isn't a money issue. It's more around some family things. He's got a son in Hamburg, obviously, and he's got a father who travels to a lot of his games, and so we've got to accommodate some of those things.”
With talks continuing since, FutbolMLS reported in late-March that a deal for a two-and-a-half seasons had been agreed but those claims now look to have been somewhat wide of the mark.
While Sporting KC still haven’t given up complete hope of making a deal happen, Vermes admits that the potential figures involved have forced the club to turn their attention elsewhere in the search for attacking reinforcements.
"It wouldn't make sense for us," the MLS Cup-winning boss said. "No disrespect to him, but it doesn't make sense for the kind of numbers we're talking.
"But is anything ever completely dead?"
Nevertheless, Van der Vaart has said this week that he would be interested in a move to the US, telling German football magazine Kicker: "Everything's open at the moment, but I can imagine playing in America. I want to keep playing at a good level for a few years.”
If Van der Vaart doesn't make the switch to MLS, though, then he won't suffer from a lack of European suitors, with the likes of Roma and former club Ajax also interested in the Netherlands international's signature, per Voetbal International.