The Taoiseach, Mr Ahern, has said he hopes to find a "shared political will" leading to an early agreement on an EU Constitution.
In a letter to fellow European Union leaders ahead of the start of the two-day European Council meeting in Brussels tomorrow, Mr Ahern said he was "convinced that we all share a sense of the importance for Europe of early agreement"
Mr Ahern is expected to circulate a report containing an account of the work done to date and an assessment of the state of play in the negotiations before tomorrow's meeting.
Negotiations on a first constitution for the EU, due to expand from 15 to 25 countries on May 1st, collapsed last December in acrimony over member states' voting powers.
But the surprise election of a more pro-European government in Spain, conciliatory statements by Poland, Germany and France, quiet diplomacy by EU president Ireland and a shared sense of a need to demonstrate cohesion have radically changed the mood.
In a symbolic move highlighting one provision of the planned constitution, the leaders will invoke a solidarity clause pledging mutual assistance in case of terrorist attack to support Spain without waiting for a final agreement and ratification.
They will issue a Declaration on Terrorism pledging to speed implementation of agreed moves such as a pan-European arrest warrant to replace lengthy extradition procedures, and back new security measures to boost police and judicial cooperation, share intelligence analysis and combat terror financing.
The Madrid bombings were "a chilling reminder that the threat posed by terrorism affects all of us and requires a common European Union response", Mr Ahern said in the letter, published on the EU Presidency website.
Mr Ahern aims for a procedural agreement this week to conclude the constitutional treaty by the end of June, when Ireland's presidency ends.
