Iran is trying to force shippers to comply with a new protocol for transiting the Strait of Hormuz — or risk attack.

Tehran has laid out a set of new rules for vessels seeking to transit the strait, according to a document seen by CNN, pressing ahead with efforts to formalize control over the waterway in defiance of US warnings.

Entitled “Vessel Information Declaration,” the document is an application form issued by Iran’s newly created Persian Gulf Strait Authority (PGSA) and must be completed by all transiting vessels to ensure safe passage. It was shared with CNN by Lloyds List and another shipping industry source who wished to remain anonymous.