BRUSSELS, April 18 (Reuters) - Poland this month presented a proposal for a new set of sanctions against Russia for waging war against Ukraine, according to a document seen by Reuters on Tuesday, including a ban on pipeline oil and diamond imports. The EU's chief executive, European Commission President Ursula von der Leyen, has said previously an 11th package would focus on combating circumvention of existing restrictions, in particular for spare parts and equipment that Russia deploys on the battlefield against Ukraine. See here for a complete list of exchanges and delays