Inverness are facing a fight to keep hold of Niculae and have already turned down two bids from Turkish outfit Kayserispor and Greek side PAOK Thessaloniki.
Director of football Graeme Bennett confirmed Kaiserslautern had expressed their interest in Niculae.
"We have had an inquiry from Kaiserslautern. They have not made a bid although they said they were going to," Bennett told the Press & Journal.
"I met with Marius last week and I said I would keep him abreast of any interest in him. I told him we received two offers and I did not think they were acceptable and he was quite happy with that.
"He played in Germany before and teams know him.
"He has played in the SPL for a season and I don't think it would be a big gamble for a team in Germany to take him, although we are not under any pressure to sell him.
"We have made a huge financial commitment with Marius and we want to make our money back.
"If no-one comes up with a realistic offer we will keep him for a second year and he is factored into our budget for this season.
"The transfer window runs until August 31 and we may have to wait until then."