* Investors lower offer to $24.50 per share from $27
* Ask CommonWealth to cancel stake sale in Select Income
* Say can negotiate a deal in 3 weeks if company agrees to talks
March 28 (Reuters) - Activist investor Keith Meister and real estate major Related Cos lowered their offer price for CommonWealth REIT to $24.50 per share from $27, citing the office building operator's recently completed equity offering.
Related and Meister's Corvex Management LP, which together own about 9 percent of CommonWealth shares, also said they would continue to pursue the removal of the company's board if it was not open to being acquired by them or another buyer.
"If you are prepared to enter into good faith negotiations with us, we could negotiate and announce a transaction in less than three weeks," Related and Corvex said in a letter to the CommonWealth board.
The activist investors oppose CommonWealth's externally managed structure under which its management is compensated based on the assets under management, not profitability.
Related and Corvex proposed to buy CommonWealth last month, subject to the company cancelling its share offering that they said was "value destroying."
The company, however, went ahead with the public offering at $19 per share, raising $627.6 million. It also sold its stake in Government Properties Income Trust for $240.1 million.
CommonWealth's outstanding shares increased to 118.3 million after the offering, according to Thomson Reuters data. Based on that, the new offer would value the company at $2.9 billion.
Related and Corvex on Thursday also urged the company not to proceed with its planned stake sale in Select Income REIT as they believed the shares would be sold at a discount.
"Our offer is subject to further downward adjustment if you move forward with a sale of all or a portion of CommonWealth's controlling stake in Select Income," the investors said.
Corvex and Related would be prepared to buy a controlling stake in Select Income at a premium value if the REIT's current trustees resign and its management agreement with its external adviser, REIT Management & Research LLC (RMR), is terminated. RMR also owns interests in other publicly traded REITs.
The investors, which have the support of other large shareholders Luxor Capital Group and Perry Capital, said they had met Barry and Adam Portnoy from the Commonwealth management team earlier this week, following a request made by the two firms on Feb. 25.
CommonWealth's shares were trading at $22.31 on Thursday on the New York Stock Exchange. Select Income shares were up 2 percent at $54.10.