Despite being United's top goalscorer in 2016-17, Ibrahimovic was released by the Premier League giants after suffering a serious knee injury in April.
There has been speculation that United could offer Ibrahimovic a new contract if the 35-year-old proves his fitness as he completes his rehabilitation at Carrington.
And Ibrahimovic's future could be resolved soon after the Swedish star was quoted as telling photographers: "There will be a very big announcement soon, it will be huge."
But whether Ibrahimovic's future includes the five-time MLS Cup champion Galaxy remains to be seen.
Ibrahimovic was linked with the Galaxy before joining United from Paris Saint-Germain last year.
Responding to growing speculation on Thursday, Onalfo told reporters: "Our policy is not to comment on players that are not part of our team."
Asked whether the Galaxy – who have lured David Beckham and Steven Gerrard to StubHub Center in the past – had space for a marquee, Onalfo said: "Absolutely. We always have. The DNA of the Galaxy is to attract world-class players, so we're always looking for one."