Former Arsenal star Song will miss three months with ankle trouble, leaving the ex-Cameroon midfielder haggling with the Hammers over the length of a permanent contract.
Song spent last season on loan at Upton Park, and Barcelona are ready to let him return on a free transfer – but new West Ham boss Bilic admitted talks are ongoing with the 27-year-old.
“We are in contact but it’s not for the media yet,” he said.
West Ham will face Romanian outfit Astra Giurgiu at Upton Park on Thursday as their marathon pre-season continues apace.
Hammers manager Bilic again admitted frustration with the packed schedule brought about by an unexpected Europa League qualification bid.
West Ham have been linked with a £12million bid for Fenerbahce striker Moussa Sow, and Bilic admitted the club are still in the market for two more recruits before the start of the new Premier League season.
“We are not panicking, we are good: if we can find a player, or maximum two, who are going to make us better then we definitely want to do it,” he said.
“We have to like the player, and the player has to be free, or payable and a good investment for the club.
“I’m happy with my squad, the transfer window is still very open and there’s a possibility some players will come and some will go.”
West Ham face their 10th game of the pre-season already on Thursday – with two more to follow after that before they start their Premier League campaign with a testing trip to Arsenal on August 9.
Former Hammers defender Bilic vowed he will not allow his side’s lengthy run-up to the league season to account for any fatigue.
“It’s not ideal, but there’s no point moaning or saying it again, we just have to cope with the situation and that’s it – no excuses,” he said.
“I would have had to learn quickly here anyway, because I’m new here.
“I’ve done my homework but these European nights we’ve had so far, they are not ideal, but at the same time they give you the best pictures from your players.
“The negative side of that was that we had so many games because the club had to arrange friendly matches because we didn’t know we’d compete in European qualification.”
Bilic hopes West Ham can take control of their two-leg battle with Astra Giurgiu on Thursday – to allow him to mix up selection for the return clash in Romania a week later.
“They are a club that’s investing money, has a lot of good players,” he said.
“Last year they knocked out Lyon so it’s going to be a good test for us.
“I’m hoping for that (a commanding victory) and it would be nice, and we’re going to try for that, but to be fair we’re not expecting an easy ride.”