"We don't want more aid... but we need breathing space," Samaras said after talks with Merkel.
"I am sure our plan will soon bear fruit. We will hit our targets," vowed Samaras, speaking through an interpreter, adding: "Actions speak louder than words."
"We are at the beginning of a new phase in relations between our two countries," said the Greek prime minister, as ties had become strained between Berlin and Athens as a result of the near three-year eurozone debt crisis.
Merkel stressed she wanted debt-wracked Greece to remain in the eurozone and said she believed the country's government was doing all it could to solve its problems.
"I want Greece to remain part of the eurozone," Merkel said as she welcomed Prime Minister Antonis Samaras for talks in Berlin. “The euro is more than a currency – it is the idea of a united Europe,” she said.
But German people are losing patience with the Greeks, a survey released on Friday suggested. Two thirds were against the idea of giving Athens more time to make the savings needed, while 72 percent rejected any suggestion of increasing the aid package, the poll conducted for ZDF broadcaster showed.
"I am deeply convinced that the new Greek government, under the leadership of Prime Minister Samaras is doing everything to solve the problems that Greece is facing," Merkel told reporters.
"We know that this requires great sacrifices... and Germany has always said that it will support Greece in this.
Samaras is on a two-day trip to Berlin and then to Paris with his debt-wracked country's future in the 17-nation eurozone in the balance as its cash reserves dry up and a new injection of European funds hangs by a thread.
Ahead of his arrival in Berlin, Merkel and French President Francois Hollande urged him to push through with the reforms.
The pair sent the clear message as they went into a working dinner to discuss the euro crisis and Greece in particular before each meets the Greek prime minister separately in coming days.
"It is important for me that we all stick to our commitments... but I will encourage Greece to continue along its path of reforms," Merkel said in a brief statement on Thursday after greeting Hollande with kisses on both cheeks.
Hollande said he wanted Greece, which is struggling under crippling debt in its fifth year of recession, to remain in the 17-country bloc but that it was in the hands of the Greeks themselves.
"I want Greece to stay in the eurozone," he said, adding however: "It's up to the Greeks to make the necessary efforts so that we can achieve this goal."
Merkel said she and Hollande would also discuss how to implement decisions taken at the European level on banking supervision, the current crisis in Syria and a treaty marking 50 years of Franco-German cooperation.
"We won't be bored," Merkel quipped, referring to their packed agenda.
In return for the €31.5 billion installment, Athens has committed to €11.5 billion of spending cuts for 2013 and 2014, a period that Samaras reportedly wants to extend by two years.
Merkel has repeatedly said Greece must stick to what it signed up to and the message was hammered home Thursday by her finance minister.
"More time is not a solution to the problems," German Finance Minister Wolfgang Schäuble told SWR public radio, adding: "More time would, in case of doubt, mean more money."
After meeting Samaras Wednesday, Eurogroup chief Jean-Claude Juncker said Greece's place was in the eurozone but urged its government to redouble reform efforts to secure continued EU-IMF financial aid, warning it was Greece's "last chance."
"As regards the lengthening of the adjustment period, it will depend on the findings of the troika mission," Juncker said referring to auditors from the European Commission, European Central Bank and International Monetary Fund.
The foreign ministers of Germany and the three Baltic states have jointly warned the debt crisis risks splitting Europe between north and south in an echo of the Cold War division.
The chancellor, entering the countdown to elections by October 2013, faces resistance at home to granting Greece more aid after nearly three years of the eurozone lurching from one crisis to another.
But at the helm of Europe's effective paymaster, she has been under pressure to chart decisive action to shake off the debt crisis, inspire confidence in the markets and keep the bloc intact.