CARACAS, Jan 20 (Reuters) - Venezuelan state oil company Petroleos de Venezuela last month sent letters to joint venture partners asking if they wish to maintain stakes in their various projects once they expire, four people familiar with the matter said on Wednesday.

Contracts for many of the ventures expire in 2026, with the option to renew for 15 years. The negotiation period for the potential renewal begins five years before the expiration date, said the people, who described the communications as procedural.

The letters come as PDVSA's crude production has fallen to its lowest level in decades at just 434,000 barrels per day, due to years of underinvestment and mismanagement, and more recently U.S. sanctions aimed at ousting President Nicolas Maduro.

The sanctions have complicated many private partners' ability and willingness to invest in the projects' operations. Cash-strapped PDVSA has for years lacked sufficient resources to invest enough to prevent output from falling.

PDVSA did not immediately respond to a request for comment.

Partners at the company's dozens of joint ventures include Chevron Corp, China National Petroleum Corp, Italy's Eni and France's Total. PDVSA has majority stakes in all its crude joint ventures, as required by Venezuelan law (Reporting by Deisy Buitrago in Caracas, Luc Cohen in New York and Marianna Parraga in Mexico City; editing by Richard Pullin)