(Adds details on Egypt borrowing capacity, Ukraine, Zimbabwe)

By David Lawder

WASHINGTON, July 28 (Reuters) - The International Monetary Fund said on Thursday that the size of Egypt's financing program will be determined by a two-week IMF mission to Cairo starting this weekend.

IMF spokesman William Murray declined to confirm the Egyptian finance ministry's estimate of a $12 billion loan program spread over three years after it requested IMF support earlier this week.

"The scale of IMF financing will depend on the mission team's assessment during the visit of the financing needs and the strength of the authority's reform program," Murray told a regular biweekly news briefing.

He noted that Egypt's quota, or shares in the Fund, are about 2.08 billion Special Drawing Rights - the IMF's unit of account - or about $2.9 billion at current exchange rates.

Under normal access to IMF programs, member countries can borrow up to 145 percent of their quota for any 12-month period. That would be about $4.2 billion based on Egypt's quota level. Countries with normal access can borrow 435 percent of their quotas over the life of the program, which would total about $12.6 billion in Egypt's case.

Regarding Ukraine, Murray said the Fund's executive board would not vote on a release of the next portion of the country's $17.5 billion until at least mid-August, after the board returns from a two-week break. The Fund earlier had said that a review on unlocking the next $1.7 billion tranche was nearing completion and it could be considered in July.

Murray added that there was no change in the IMF's engagement with Zimbabwe that would allow for negotiations on a support program to begin. Zimbabwe must first clear its arrears with the institution, Murray said, adding that he had no details of any concrete actions by Zimbabwe to do so.



(Reporting by David Lawder Editing by W Simon and Dan Grebler) ((David.Lawder@tr.com; +1 202 354 5854; Reuters Messaging: david.lawder.thomsonreuters.com@reuters.net))