By Francesco Guarascio and Robin Emmott BRUSSELS (Reuters) - The European Union will try to reach an agreement on Monday to tackle the migrant crisis in the Mediterranean despite resistance from Spain and Poland, who say they are not ready to absorb large numbers of new asylum seekers. Following the deaths of some 700 people on a fishing boat heading for Italy from Libya in April, the European Commission, the EU's executive, has proposed a plan to keep more migrants from attempting the dangerous crossing. Despite an agreement among EU leaders at a summit in June, Spain and Poland have emerged as the staunchest critics of a relocation plan, opposing the number of asylum seekers they are expected to take in from Italy and Greece.