Procedures for a voluntary swap of privately-held Greek government bonds for longer maturity paper will start in August, Greece's deputy finance minister said on Tuesday.

Greece's private sector creditors will take a 21 percent loss on their bond holdings as part of a 37 billion euro contribution to a rescue plan for the debt-stricken country, agreed at a euro zone summit last week.

In the coming days, in collaboration with (bank lobby) IIF, talks outlining the exact procedure that will be followed so that holders of Greek government bonds choose one of four options and proceed to a debt swap will be completed, Deputy Finance Minister Filippos Sachinidis told Mega TV.

Yes, this procedure will start in August, he said.

The International Institute of Finance (IIF) has estimated a take-up rate of about 90 percent for the voluntary program, which gives banks the option to swap Greek debt with new bonds with maturities of up to 30-years.

Officials want to conduct the voluntary bond swap quickly to minimize the period during which Greece is expected to be in partial default.

The goal is for this (bond swap) to last as briefly as possible, Sachinidis said. It appears that we will manage to secure a satisfactory participation to proceed with the exchange.

On Monday, IIF's chief Charles Dallara, who met with visiting Greek Finance Minister Evangelos Venizelos, said the voluntary bond swap of Greek debt was predicated on continued IMF financial support.

Greece said on Monday that the first working meeting on implementing the private sector's involvement under the new rescue deal will take place in Athens on July 28.

(Reporting by George Georgiopoulos; editing by Patrick Graham)