Plans for an EU-Africa summit have been on hold for years because Britain and other EU countries have refused to attend if Mugabe is there, while African countries have refused to come if he is barred.
Some EU officials have suggested Zimbabwe could be represented at a lower level than Mugabe, perhaps by the country's foreign minister.
"It's useful to have him (Mugabe) there for the dialogue to go on," Commonwealth chief Don McKinnon told Reuters in an interview on Tuesday during a two-day visit to Brussels. "Africa's relation with the EU is very important."
"If the dialogue gets cancelled because Africa refused to get on with the request (to veto him), it would be a bigger problem."
Zimbabwe left the Commonwealth in 2003 after being suspended the previous year. The body groups Britain and 52 mostly former British colonies, 18 of which are African nations.
Portugal, the current EU president, is keen to improve relations between the bloc and Africa and has said it will not discriminate among African states.
But diplomats say some EU leaders such as Britain's Gordon Brown are not keen to share a forum with Mugabe.