UPDATE 1-Venezuela's PDVSA says it guarantees investor security amid uncertainty

uncertainty@ (Adds PDVSA quote, context on political turmoil)

CARACAS, July 10 (Reuters) - Venezuela's PDVSA is guaranteeing "legal security" for all foreign companies in the leftist-run nation, the state oil producer said in a statement, rebuffing a government adviser's suggestion that their operations could be nationalized.

The statement, which was distributed to its joint venture partners and which Reuters saw, comes after a prominent government-allied lawyer said a new legislative body could rewrite parts of the constitution to ensure the state has full ownership of the oil industry.

The new "constituent assembly" would supersede other institutions and has sparked fears that President Nicolas Maduro's unpopular administration could take aim at joint venture partners, which include large oil companies Chevron Corp and Rosneft.

But PDVSA, whose full name is Petroleos de Venezuela, was quelling fears that a more radical wing of the ruling Socialist Party could be out to nationalize companies, as late leader Hugo Chavez did a decade ago.

PDVSA "guarantees legal security to investors, partners, and others," the statement read. "In the case of joint ventures, PDVSA has honored and will continue to honor the legal norms that allow the possibility of doing business with private companies." (Reporting by Alexandra Ulmer; Editing by Lisa Von Ahn)