The political agreement signed Wednesday in Athens authorizes the construction of TAP through the three countries should it be selected as the preferred route to Europe for natural gas produced in the Caspian Sea fields of Azerbaijan.
Samaras hailed the agreement as "a very important step indeed" for Greece, declaring it would upgrade its geo-strategic role in Europe and the world's energy markets "for decades."
The "trilaterial intergovernmental agreement" on TAP was signed by Greek Foreign Minister Dimitris Avramopoulos, Albanian Deputy Prime Minister Edmond Haxhinasto and Italian Economic Development Minister Corrado Passera, Kathimerini reported.
It sets out the legal framework for the pipeline and includes a range of commitments by Greece, Italy and Albania to ensure they work together in the developing the route.
TAP is competing with the Nabucco West proposal to bring Caspian Sea gas to Europe along a "southern gas corridor," thereby lessening Europe's dependence on Russian supplies.
The TAP consortium, led by Switzerland's Axpo, Norwegian major Statoil and German energy company E.ON, say the 500-mile pipeline system would start out with an annual capacity of 10 billion cubic meters of natural gas.
Under the current plans, it would start in Komotini, Greece, traverse Albania and then go undersea to Italy, when it would connect with existing infrastructures.
TAP last year was selected by the Shah Deniz Consortium in Azerbaijan as the preferred pipeline should they decide to favor a southerly route, while Nabucco West -- a 1,450-mile pipeline across Bulgaria, Romania and Hungary to Austria -- got the nod if Central European route is chosen.
The BP-led consortium is expected to make a final decision in June.
"A southern route will give special weight to the participating countries and will increase the geopolitical importance of the region in general," Samaras said. "The implementation of the TAP pipeline will transform Greece for the first time from a minor transit country in trans-European energy networks."
European Energy Commissioner Gunther Oettinger also praised the trilateral agreement Wednesday.
"This pipeline is instrumental to connect the gas markets of Italy and Greece and to bring gas to Albania and potentially to other of our Energy Community neighbors," he said.
"It could be among the first components of the southern gas corridor which aims at linking directly the European Union with the rich gas sources in the Caspian Region."
The Albanian government approved the TAP agreement last week, bringing similar predictions of benefits to the impoverished nation.
Albanian Prime Minister Sali Berisha called the step a "historic" one for his country, the Tirana daily Tema reported.
"The advantages of this project are enormous," he said. "Albania would take a central position in the field of energy in the region since its geographical position is very important."
Combined with a hydropower plant along the River Devoll being built by a joint venture between Austria's EVN AG and Norway's Statkraft AS, TAP has the potential to transform Albania into a developed country, he said.
"Who could ever have imagined that the two biggest projects in the history of the country would be because of the countries of northern Europe and Norway?" the prime minister said.