April 9 (Reuters) - Activist investor Jonathan Litt's Land & Buildings Investment Management nominated two directors to National Health Investors' NHI.N board on Wednesday, escalating a proxy battle with the medical real-estate firm.

Land & Buildings, which owns about 1.3% of outstanding shares in NHI, urged the medical real-estate investment firm's shareholders to elect Adam Troso and Jim Hoffmann at an annual stockholder meeting on May 21.

Hoffman is a former partner and senior vice president of Wellington Management Company and Troso is a former managing director at J.P. Morgan and Greenhill in Real Estate Investment Banking, Land & Buildings said.

Litt launched a proxy fight at NHI in February and sought to oust two board members, according to a media report.

The activist firm said on Wednesday that NHI's stock has underperformed due to the company's structure and its board being closely tied to one of its largest tenants, National Healthcare NHC.A.

Last year, it urged National Health Investors' shareholders to vote against two directors at the company's 2024 annual general meeting.

NHI said on Tuesday that Land & Buildings has proposed no new ideas for its business or strategy and added that their demand to pick candidates was "unwarranted."

The company has a market capitalization of about $3.21 billion, according to data compiled by LSEG.

NHI did not immediately respond to Reuters' request for comment.

(Reporting by Anshuman Tripathy in Bengaluru; Editing by Shinjini Ganguli)

((Anshuman.Tripathy@thomsonreuters.com;))