The opposition's pullout from Friday's vote raises pressure on Zimbabwe's leader.
Political commentators and ordinary Zimbabweans say the opposition Movement for Democratic Change's decision Sunday will save lives.
Despite Russian and Serbian opposition, UN Secretary-General Ban Ki Moon said Friday the UN would gradually cede its role.
Meeting in Brussels, European Union leaders signaled their intent to ensure that all 27 member states ratify the key treaty, which governs EU decisionmaking. But Czech approval also appears in doubt.
The E.U. voted to allow longer detentions for illegals and to standardize deportation rules.
The incentive program marks a shift in Spain's lenient immigration policies.