Egypt has signed a non-disclosure agreement with the Japanese owner of a megaship that blocked the Suez Canal in March as it finalises a compensation agreement, the canal authority chief said.

Egypt has been seeking hundreds of millions of dollars in compensation from Japanese firm Shoei Kisen Kaisha for lost canal revenues and the costs of salvaging the ship and repairing the damage to the canal.

It slashed its initial claim for $900 million to $550 million late last month but the final amount has been the subject of tough negotiations between the two sides.

"What we signed is a non-disclosure agreement" regarding the amount of the compensation, Suez Canal Authority chief Osama Rabie told Egypt's DMC television channel late Wednesday.

"A final deal is expected to be reached and announced in the middle of next week."

One of the vessel's insurers, UK Club, said an agreement in principle had already been reached and the two sides were now working to finalise a signed agreement as soon as possible.

The 200,000-tonne MV Ever Given got stuck diagonally across the canal during a sandstorm on March 23, blocking the vital trade artery for six days before salvage teams could dislodge it.

Egypt lost between $12 million and $15 million in revenues for each day the waterway was closed, according to the canal authority.

The grounding of the ship and the intensive salvage efforts needed to refloat it also resulted in significant damage to the canal, which Egypt wants to be compensated for.

Last month, President Abdel Fattah al-Sisi approved a major expansion of the canal to avoid future blockages.