Greece announced on Tuesday the key terms of the voluntary write-down of part of its sovereign debt owned by private bondholders, a few hours after a euro group meeting in Brussels sealed the second bailout package for the country to avoid a default next month.

The transaction under the Private Sector Involvement (PSI) plan agreed initially at the October 26 euro zone summit "is expected to include private sector holders of approximately 206 billion euros (272.89 billion U.S. dollars) aggregate outstanding face amount of Greek bonds," said a press release issued by the Greek Finance Ministry.

After marathon talks since late 2011, banks and hedge funds reached a deal with Greece to eventually accept losses of 53.5 percent on the nominal value of the Greek state bonds they currently hold. The October 26 agreement had paved the way for a 50-percent "haircut."

Private sector creditors are expected to swap the bonds for new ones with longer maturities at coupons starting from 2 percent annually until 2015 to 4.3 percent annually after 2020, according to the announcement.

European officials and analysts expect that some bondholders might not be satisfied with the final deal. For such case, the Greek government will shortly submit to the Greek parliament a draft bill which will introduce a collective action clause to be used in the implementation of the PSI transaction if necessary to achieve participation at the levels anticipated by the October 26 summit, added the announcement.

"A successful PSI transaction is required to bring Greece's debt-to-GDP ratio on a downward path reaching 120.5 percent by 2020. It is also a condition for the continued disbursements by the official sector, which are essential for the implementation by Greece of its economic reform program," said Greek Finance Minister Evangelos Venizelos.

Under the heavy burden of some 160 percent of its GDP over the past two years, since the start of the acute debt crisis, Greece depends on multi-billion euro rescue loans by European counterparts and International Monetary Fund to avoid a bankruptcy that could send shockwaves across the global economy.

The initial target to secure the 130 billion euro ( 172.21 billion U.S. dollars) package, the second since May 2010, was set at a reduction of the debt to 120 percent of GDP by 2020.

However, the wider involvement of the private sector has opened the way for the agreement on the bailout package and the bond-swap process on time.

A 14.5 billion euro ( 19.21 billion U.S. dollars) bond repayment is due on March 20 and after Tuesday's positive outcome, Greece is expected to be able to escape a financial collapse.