(Corrects paragraph 5 to delete reference to ShoreTel rejecting Mitel's offer. ShoreTel did not say it rejected the offer.)
Oct 20 (Reuters) - Canadian telecommunications provider Mitel Networks Corp made public its about $540 million offer for smaller U.S. peer ShoreTel Inc.
Mitel's cash offer of $8.10 per share represents a 24 percent premium to ShoreTel stock's closing price on Friday.
Sunnyvale, California-based ShoreTel's shares were up 18 percent at $7.76 - below the offer price - in heavy volumes in mid-day trading. They touched a high of $7.80 earlier.
Kanata, Ontario-based Mitel said it made its offer public after ShoreTel's board rejected an earlier proposal - also for $8.10 - sent on Oct. 2 and refused to engage with the company.
ShoreTel said on Monday it would review the proposal in consultation with its financial and legal advisers.
Mitel's shares fell about 2 percent to C$9.25 on the Toronto Stock Exchange, while its Nasdaq-listed shares were also down about 2 percent at $8.20.
Mitel Chief Executive Richard McBee said a deal would bring together two companies "with strong and complementary market footprints, particularly in the U.S. where ShoreTel does more than 90 percent of its business."
Mitel said its offer would remain open until 5:00 p.m. ET on Nov. 20.
Blackstone Advisory Partners is the financial adviser to ShoreTel.
Mitel in November bought smaller Canadian rival Aastra Technologies Ltd in a deal for C$392 million ($374 million) to expand in Europe. (Reporting by Narottam Medhora and Swetha Gopinath in Bangalore; Editing by Simon Jennings and Sriraj Kalluvila)