RIO DE JANEIRO, Nov 22 (Reuters) - Brazilian state-run oil firm Petrobras is looking into potential tie-ups to speed up its plans to boost Brazil's fertilizer output, two sources close to the matter said.

One option would be to find a partner that would complete construction on a fertilizer plant in Mato Grosso do Sul state that had its works halted, one of the sources said.

Companies such as Norway's Yara or China's Sinochem are on Petrobras' radar, said the source.

Brazil relies on imports to meet its fertilizer needs and boosting local production is one of the requests President Luiz Inacio Lula da Silva made for the firm's next strategic plan, scheduled to be unveiled on Friday.

Petrobras has also leased two fertilizer plants to Unigel , and is in talks with the firm, including regarding a project related to green hydrogen.

One of the plants, located in Bahia state, is currently out of operation.

Unigel said that it was in open negotiations with Petrobras, but that it would not comment any further at the moment. Yara said it does not comment on market rumors, while Petrobras and Sinochem did not immediately respond to requests for comment.

"How long will Brazil be dependent on imports of such an important input for our agribusiness? Something has to be done, and we think it will be," said the second source, who added that natural gas prices are a "major obstacle" for local fertilizer production. (Reporting by Marta Nogueira and Rodrigo Viga Gaier; Writing by Peter Frontini; Editing by Sandra Maler)