Finland's foreign minister, whose country holds the EU presidency, says he would like to see fresh UN troops deployed in Lebanon within a week.
Many Lebanese are returning to find homes damaged or destroyed
Erkki Tuomioja was speaking as he made whistlestop visits to France and Germany to discuss Europe's contribution to the peace force.
France will reveal later on Thursday if it is boosting its 200 extra troops.
Meanwhile, the UN has launched what it calls a 60-day plan to tackle the humanitarian situation in Lebanon.
Hundreds of thousands of people have returned to southern Lebanon to find their homes destroyed or badly damaged and have no access to proper sanitation or drinking water, UN emergency relief co-ordinator Jan Egeland said.
Pressure has grown for the expanded UN force - which should eventually include 15,000 troops - to be quickly deployed to southern Lebanon to monitor the fragile ceasefire, now in its 11th day.
The UN has been disappointed by the response of European nations, which in turn have expressed concern about the force's mandate, particularly on the issue of disarming Hezbollah.
"We would like to see the first reinforcements arrive within a week if possible," Mr Tuomioja said in Germany before leaving for Paris.
"The main thrust of the force should be there within a few weeks," he said, before adding that a full deployment may take months.
Earlier, he told the BBC Today programme that "in total we would hope that of the 15,000 almost a half would come from EU member states".
In Paris, French President Jacques Chirac will announce later what decision France has taken about boosting its initial contribution of 200 fresh troops.
France has faced criticism over its offer - it had initially been expected to provide the backbone of the UN force in its former colony.
Italy's readiness to play a leadership role - and its pledge of up to 3,000 troops - was welcomed by Mr Tuomioja.
He said there would be a clearer idea of contributions from EU member states on Friday, adding: "It's understandable that each one has at the end of the day to make their own decisions, in their own parliaments."
Israeli foreign minister Tzipi Livni, speaking after meeting her Italian counterpart in Rome, called the ceasefire resolution "a window of opportunity" for the region.
But she said the international community must show it is prepared to act. "There is a big question whether the international community is willing to show determination in order to implement its own decision," she added.
The flurry of diplomacy comes a day before a special meeting of EU foreign ministers, which will be attended by UN Secretary General Kofi Annan in Brussels.
Mr Annan will seek to "reassure" potential contributors that the force is not being sent "to disarm Hezbollah by itself or against the will of the Lebanese people," his spokesman Edward Mortimer said.
The UN chief will also "emphasise the urgency", he added.
"There is a political solution attainable there. Without the force on the ground the political solution will probably not be attainable," Mr Mortimer told the BBC.
Political tensions have risen over the possible deployment of UN troops in the border area of Lebanon and Syria.
Syrian President Bashar al-Assad warned it would be considered a hostile move, while Mr Tuomioja said his Syrian counterpart told him Syria would close its borders if the deployment happened.
Israel has indicated it will not lift its air and sea blockade on Lebanon until international peacekeepers take up positions along the border. It accuses Syria of supplying arms to Hezbollah across the border.
Relief workers are now able to reach most of those areas of southern Lebanon that were cut off during the conflict.
Most of the one million people who fled the area have now returned, but many still have no proper access to basic utilities, Mr Egeland said.
"Food is in general less of a problem than water and sanitation. We also have probably hundreds of thousands who come back and see that their housing is either destroyed or badly damaged," he told the BBC.