SAO PAULO/LONDON, March 4 (Reuters) - Brazilian sugar and ethanol producer Raizen said on Wednesday it is analysing a proposal for a Shell-led 4 billion real ($765 million) capital injection, while indicating that a solution to its debt crisis could be implemented in an out-of-court restructuring process.

Raizen, a joint venture between Shell and Brazilian conglomerate Cosan ( CSAN ), has been discussing with creditors and shareholders for months how to strengthen its capital structure and address billions of dollars of debt.

In a securities filing, Raizen said the proposal currently under analysis includes a capital contribution of 3.5 billion reais from Shell, plus 500 million reais from an investment vehicle owned by the family of Rubens Ometto, Cosan's ( CSAN ) controlling shareholder.

Raizen, which said its financial restructuring process could also include a debt-to-equity swap and asset sales, did not mention any capital injection proposed by Cosan ( CSAN ).

While Cosan ( CSAN ) has said it is prepared to contribute 1.5 billion reais - including the 500 million reais from Ometto - it is unable to match Shell's proposed investment, two sources told Reuters earlier on Wednesday.

An unmatched capital injection from Shell would dilute Cosan's ( CSAN ) stake, but the extent of the dilution would depend on how much debt is converted into equity in negotiations with creditors, another person said. 

Raizen could end up under the control of Shell, sources said, after rescue talks between the joint venture partners and creditors collapsed this week.

Cosan ( CSAN ) declined to comment before the filing from Raizen, and Shell did not immediately respond to a request for comment.

Raizen, one of the world's largest ethanol producers, has posted a string of losses and its debt has ballooned in recent quarters. In February, the world's top sugar producer warned of "significant uncertainty" over its ability to continue operating, prompting owners and creditors to scramble to shore up the company. 

Raizen said in the filing that it intends to ensure a "protected and orderly environment" that allows discussions with financial creditors for a debt solution. The firm said the potential solution "may, if necessary, be implemented through an out-of-court restructuring process".

Raizen's net debt rose to 55.3 billion reais by the end of December due to a combination of elevated investment spending, erratic weather and wildfires that hurt harvests and reduced cane crushing volumes.

($1 = 5.2810 reais)