Foreign ministers and other officials from 18 nations, as well as the United Nations Secretary-General Kofi Annan, gathered at Italy's Foreign Ministry for a meeting expected to last just a few hours.
Under discussion will be calls for a ceasefire and the possible deployment of a multinational force to stabilise Lebanon's border with Israel and help disarm Hezbollah guerrillas, European Union officials said.
The push for an immediate ceasefire, however, is running into strong opposition from the United States and Britain, which insist that any truce must lead to a durable peace and ensure that Hezbollah is no longer a threat to Israel.
An Israeli airstrike on a UN observation post in southern Lebanon that killed at least three unarmed UN observers could further fuel international demands for a quick end to the fighting.
UN Secretary-General Kofi Annan said the airstrike late yesterday appeared to be a deliberate attack and demanded an investigation.
Israeli Prime Minister Ehud Olmert called Mr Annan today to express his "deep regret over the mistaken killing," Mr Olmert's office said.
Rapid reaction force
Officials in Brussels told The Associated Press that Javier Solana, the EU foreign and security affairs chief, will propose that a rapid reaction force be established.
It would ideally be built around French, German and Spanish troops, supplemented by forces from Turkey, the Netherlands, Canada and Arab states such as Egypt and Saudi Arabia, EU officials said.
Mr Solana said yesterday that an international force for Lebanon should represent a broad sweep of nations to generate the widest possible public support in the Middle East and have a robust United Nations mandate to use force, if necessary.
He gave no details of timing or duration of any peacekeeping mission.
The closed-door Mideast meeting brings together 18 nations and international organisations seeking ways to end the fighting between Israel and Hezbollah militants based in southern Lebanon.
Ceasefire 'main goal'
Italian Premier Romano Prodi said the main goal of the conference is a ceasefire between Israeli troops and Hezbollah guerrillas, along with discussing an international force and the problem of refugees, which he said was of "astonishing
proportions."
US Secretary of State Condoleezza Rice reiterated the United States' position that a cessation of hostilities in Lebanon must come with conditions, saying there is "no desire" on the part of US officials to come back in weeks or months after terrorists find another way to disrupt any potential ceasefire.
Shortly before the conference, secretary Rice met with Italian Foreign Minister Massimo D'Alema.
Yesterday evening, she had dinner with Lebanese Prime Minister Fuad Saniora, Mr Annan and Mr Solana.
Mr Annan left the hotel briskly as reports broke about the bombing of the UN observer post in southern Lebanon.
Mr Annan has said he wants the Rome conference to agree on a package to stop the Israeli-Hezbollah fighting and ensure lasting peace between Israel and Lebanon.
In the short term, he said, urgent measures are needed to halt the violence and get humanitarian aid to the Lebanese uprooted by the fighting. But the package should also include a ceasefire, deployment of an international force and the release of two Israeli soldiers abducted by Hezbollah, he said.
The United Nations already has a peacekeeping force of 2,000 military personnel in Lebanon - called UNIFIL - with a mission to patrol the border.
Multinational peacekeeping force
Some countries have expressed support for a new multinational peacekeeping force, most notably Britain, which hopes the Rome meeting will produce an agreement in principle on setting up a stabilisation force.
Italy, host of the conference, has said it would support the idea of a multinational force and participate in one provided there was a strong mandate from the United Nations.
Israel - which had so far called for the Lebanese army to take control of the area - signalled a policy shift when it said on Sunday that it would accept a new international force, preferably from NATO.
But Germany said yesterday that a ceasefire must be in place before there can be any thought of sending international troops to Lebanon.
Syria not invited
The foreign minister of Syria, a country that is a key supporter of Hezbollah, said in an interview published today in the Italian newspaper La Repubblica that his country was "ready to intervene to carry out a constructive role," but he demanded that "the United States press Israel so that it accepts a ceasefire and a prisoner exchange."
"We have not been invited (to the Rome conference) but our position is clear: We demand a ceasefire that allows for the diplomatic activity to begin," Walid Moallem was quoted as saying.