* Cos to explore upstream oil, gas opportunities in Mexico
* Cos to also jointly explore international markets (Adds details from statement, background)
MUMBAI, Dec 5 (Reuters) - India's Reliance Industries Ltd said on Friday it has entered a pact with Mexico's national oil company Petroleos Mexicanos (Pemex) to explore potential upstream oil and gas business opportunities in that country.
The deal comes as Mexico, the world's tenth-largest crude producer, is implementing sweeping reform of the energy sector that was approved earlier this year and that ended Pemex's decades-long monopoly.
Mexico's energy regulator last month said it seeks to lure over $50 billion in investment through 2018 to stem long-sliding crude production. Current production in Mexico is around 2.35 million barrels per day.
Pemex and Reliance, controlled by India's richest man, Mukesh Ambani, will also explore international markets for "value added opportunities", the Indian energy conglomerate said in a statement.
Mexico's Pemex has been trying to expand its presence in India and other markets beyond neighbouring United States. The Mexican oil giant has said it sees India and China as future growth markets for crude.
Pemex signed an agreement in September with ONGC Videsh Ltd , the overseas business unit of India's state-run Oil and Natural Gas Corporation Ltd, to explore opportunities in Mexico's hydrocarbon sector.
Pemex was unavailable to comment outside of regular business hours on Friday.
Reliance, which operates the world's biggest refinery, said its tie-up with Pemex was in line with its strategy to expand its international asset base in regions with "attractive competitive opportunities."
In June, Ambani told a shareholders meeting that Reliance, which has invested more than $7 billion on joint ventures in the United States, was looking to expand its international presence beyond the world's largest economy.
Shares in Reliance, India's third-most valuable company with a market capitalisation of more than $50 billion, were up 0.4 percent at 961.90 rupees at 0438 GMT, while the main Mumbai market index was up 0.1 percent. (Reporting by Zeba Siddiqui in Mumbai; Editing by Sumeet Chatterjee)