Meeting in Moscow, Russian President Vladimir Putin and his Argentinian counterpart, Cristina Fernandez de Kirchner, have declared a "comprehensive strategic partnership" between the two countries.
Putin and Kirchner oversaw the signing of a series of framework agreements on energy cooperation following talks on April 23.
The agreements include Moscow's pledge to finance a hydropower plant in Argentina and a cooperation deal between Russian energy giant Gazprom and Argentina's YPF state oil company.
The countries also pledged that Russia will build a new nuclear reactor in Argentina. Rosatom nuclear corporation chief Sergei Kiriyenko said he hopes to sign the final deal by the end of the year.
Putin said the two countries also agreed to expand cooperation between their defense agencies.
Moscow aims to boost trade with Latin America to offset the effects of sanctions imposed over the Ukrainian crisis, while Argentina is looking for foreign investment as its battles U.S. hedge funds thwarting its effort to restructure defaulted debt.
Based on reporting by AFP, dpa, and the BBC