Italian, British, and Polish leaders were under constraint, the day before EU summit, to find a compromise over main differences holding up on a treaty concerning the reformation of the European Union.
European Commission President Jose Manuel Barroso urged leaders to back a draft on a new treaty, which has been hastily negotiated by lawyers and experts over the past three months.
The "Reform Treaty" is meant to replace the aborted EU constitution, which was put to rest by leaders at a June summit after it was rejected by two member nations. Instead, they agreed on the outlines of a scaled-down replacement treaty.
"I hope this will not be the battle of Lisbon," Barroso told reporters at EU headquarters in Brussels, Belgium, before flying to the Portuguese capital.
"We have a very good agreement on the table, the best on offer," Barroso said. "I therefore appeal to all governments to honor the pledges they made in June. There is no reason, no excuses, not to come to agreement."
Italy is unhappy with the reallocation of European Parliament seats in the treaty, while Poland is demanding more changes to the bloc's voting rules.
British Prime Minister Gordon Brown, meanwhile, remains under pressure to curb back his nation's participation in sensitive EU policies, notably in policing and judicial affairs.
Other last-minute problems that could scuttle the deal include a linguistic dispute launched by Bulgaria over the spelling of the word "euro" in the Cyrillic alphabet, and Austria's request that the treaty include a cap on foreign students it takes in.
Portugal's Prime Minister Jose Socrates said that reaching a final deal on the charter by Friday "is a challenge."
"Adopting the text of the Reform Treaty means not only that the European Union will be able to concentrate its efforts on questions which more directly affect and concern its citizens, but also that it will be able to do so more efficiently," Socrates said in a letter to the leaders.
Worries have risen in recent days that a deal on the treaty will be defeated because of last-minute political concerns at home.
Poland's Prime Minister Jaroslaw Kaczynski, facing national elections on Sunday, is keen to push for stronger powers for his country, notably more voting clout.
Italy's Prime Minister Romano Prodi, fearing a decline of Rome's influence in the EU, is demanding his nation keep a similar number of seats in the EU parliament compared to other big members.
Proposed changes to the European Parliament foresee the number of members drop from 785 to 750, which would mean fewer seats for 17 of the 27 EU nations.
Italy would lose the largest number of seats, 6 of 78, and would no longer have parity with France and Britain.
Bulgaria, one of the EU's newest members, complained last week that the EU's spelling of "euro" _ the European currency _ in Cyrillic is inconsistent with how it spells words such as "Europe" and "European Union," and has warned it could veto the treaty if its demands were not met.
The outline of the new draft charter came after a drawn-out and bruising three days of negotiations in June among leaders.
If agreed to, the new treaty _ a series of amendments to the EU's existing treaty rule book _ would replace the draft constitution, which was rejected by French and Dutch voters in 2005.
The constitution, which opponents saw as an attempt to create a European super-state, aimed to simplify how an expanded club of now 27 members is run. The constitution also called for a bill of rights, a flag, an anthem, a president and foreign minister, and faster decision-making to give the continent a more assertive global role matching its economic clout.
The new draft treaty scraps the title and other fetchings of a super state, but keeps the key parts _ notably a bill of rights, new voting rules, a president and a "high representative" to represent the EU abroad.