Bretton Hall, the Grade II listed former teacher training college sited next to the Yorkshire Sculpture Park, is due to be converted into a five-star venue.
Developers Rushbond and hospitality firm Artfarm, who've jointly formed the Bretton Investment Partnership, are behind the scheme. They received planning permission for the venture in May 2020.
But Wakefield Council said in July the project had been delayed because of Covid.
But the Partnership has publicly insisted the conversion will still happen and that all parties involved are committed to the scheme.
It comes a day after the council leader said she'd had assurances that it would go ahead.
A spokesman for the Partnership said: "The project has unfortunately been delayed.
"The pandemic has had devastating impacts on the hospitality industry, though we all hope that the worst is behind us.
"The partners are committed to the project."
The developers have said they want to get on with the building work as "soon as possible", and having recently secured a time extension from the council, hope to have it completed within two years.
Rushbond is already restoring the nearby Camellia House, which is on the site of the Sculpture Park and forms part of the old Bretton Hall estate.
Speaking on Tuesday on an online Q&A session, Coun Jeffery told the public that the delays were "disappointing". But she indicated she was confident the scheme would still go ahead as planned.
"It will be a great asset to us," she said.
"The developer's assured us, and I have seen evidence of this, that it will happen.
"It's been a disappointing delay, because it's a fabulous building and a fabulous area.
"Having a five-star hotel there would really bring people into our district, and bring them to the Yorkshire Sculpture Park and the Hepworth Gallery.
"So there is a delay, but it is happening. It will just be 18 months to two years."
The original Bretton Hall building was built in the 18th century, and later became a teaching college in the late 1940s.
Education there ceased in 2007, when the University of Leeds relinquished its links with the hall.
Local Democracy Reporting Service