By Abigail Summerville

NEW YORK, Oct 9 (Reuters) - MCB Real Estate has sweetened its offer to acquire U.S. shopping center operator Whitestone REIT to $1.45 billion including debt, according to a letter reviewed by Reuters on Wednesday.

The new offer from MCB would give shareholders of Whitestone $15 per share in cash, representing a 14.5% premium to Whitestone's share price on June 3 before MCB's earlier offer was disclosed.

MCB, whose earlier $14-per-share offer was rebuffed by the target, is Whitestone's third-largest shareholder, with a 9.4% stake in the company. Whitestone's shares closed at $13.47 on Tuesday.

"Our efforts to engage in constructive discussions have been rebuffed to date, but we stand ready to complete due diligence and execute a definitive agreement expeditiously and are committed to seeing this through to completion," MCB co-founder David Bramble said in the letter to Whitestone's board of trustees.

"We ask our fellow shareholders to urge the Whitestone Board to uphold their fiduciary duties and engage with us in good faith without further delay."

MCB's interest in Whitestone comes at a time when retail landlords have managed to pass on some of the recent bout of inflation to tenants, benefiting owners like Whitestone.

During the quarter ended June 30, the company witnessed an uptick in new leases, with revenues from such leases rising 34% to $16.1 million.

Limited new construction of retail real estate has contributed to the scramble for high-quality space. Vacancies at U.S. shopping centers stood at 5.3% for the second quarter ended June 30, according to commercial real estate services firm Cushman & Wakefield, the lowest level since it started tracking the data in 2007.

While Whitestone's shares have jumped 43% over the past 12 months, it is currently trading at a discount to most of its top peers, according to an analysis of LSEG data. Whitestone trades at a multiple of 14.82 times earnings before interest, taxes, depreciation and amortization, compared with 21.19 times for Acadia Realty Trust and 17.73 times for Federal Realty Investment Trust .

Baltimore, Maryland-based MCB has argued that Whitestone lags larger public REITs because it is a regional player that is hampered by high borrowing costs, making it challenging for the company to raise new capital to fund acquisitions and develop new properties.

MCB, which plans to fund its bid with a combination of equity and debt, said it was confident of securing debt financing for the proposed takeover from Wells Fargo, which is advising MCB on its bid for Whitestone.

Founded in 2007, MCB is a privately held commercial real estate developer that manages more than $3 billion in assets across industrial, office, retail and multi-family properties.

Houston, Texas-based Whitestone operates shopping centers in Texas and Arizona. Whitestone, which currently owns 57 properties with 5.1 million square feet of gross leasable area, had total debt of about $667 million as of June 30. In its latest quarter, Whitestone reported occupancy rates of 93.5%, marginally up from the same period last year.

Earlier this year, Whitestone fended off pressure from another shareholder Erez Asset Management, which launched a proxy fight at the company, nominating two new candidates to its board of trustees.

Last year, Bloomberg reported that Whitestone rebuffed a takeover offer from Fortress Investment Group.

(Reporting by Abigail Summerville in New York; Editing by Jamie Freed)

((abigail.summerville@thomsonreuters.com;))