Greek Prime Minister Alexis Tsipras on Sunday said his government will not give in to "unreasonable" demands as the debt-ridden country braces for critical negotiations with international creditors on the thorny issue of pension reform. The warning came just days after Athens got 1 billion euros under the terms of its third bailout program. The creditors - the European Commission, European Central Bank (ECB), International Monetary Fund (IMF) and the European Stability Mechanism (ESM) - finalized a third Greek debt rescue program in August worth $94 billion after Greece looked to be on the brink of crashing out of the eurozone. "The creditors have to know that we are going to respect the agreement to the letter, but that doesn't mean we are going to succumb to unreasonable and undeserved demands," Tsipras told Real News newspaper.

"We have no commitment to find the money exclusively from pension cuts. On the contrary, the agreement provides the option of equivalent measures, which we have already processed," he said. He admitted though that the pension system, which is "on the brink of collapse," needs to be overhauled. The Labor Ministry is working on a new social security system under which state-guaranteed pensions will be reportedly cut by half, to a minimum of 384 euros, and the rest will depend on a person's income and years of social security payments.