Feb 14 (Reuters) - British healthcare real estate

investment trust Assura said on Friday it had received a

preliminary approach from KKR and UK-based pension fund

Universities Superannuation Scheme.

U.S. private equity fund KKR and Universities Superannuation

Scheme, which offers principal pension scheme provided by

educational institutions for their employees, have until March

14 to make a firm offer or walk away.

"Board is currently reviewing the proposal with its

advisers" Assura said.