The summit in Rome was called by the US Secretary of State, Condoleezza Rice, and brings together European and Arab nations as well as the US and Russia.
By Bridget Kendall
BBC diplomatic correspondent, Rome
Ministers are meeting as Israel pushes into southern Lebanon
Both British and American officials have been downplaying expectations of any far-reaching conclusions.
The urgent search for a ceasefire ought to be top priority, many say.
But with the US and Britain still arguing that no ceasefire is possible without addressing root causes, that is likely to be a subject dividing, not uniting, this gathering.
Also up for discussion are ideas for further humanitarian aid for Lebanon and a multi- national force to act as a buffer between Israel and Hezbollah.
But the prospect of a peacekeeping force is also fraught with problems, not least how to persuade countries to offer troops when it is still not clear how to get agreement from either Israel or Hezbollah to stop fighting, nor what the rules of engagement of any foreign troops are likely to be.
But the very fact quite so many countries are sending so many top officials to this meeting shows just how much anxiety there is about this crisis deepening and spreading.
And even if no dramatic decisions come out of it, it may prove an important way to explore back-door diplomatic channels.
Many countries will want to know how far the US is prepared to rein in Israel at some point.
And the US will be looking to Arab countries, Turkey and Russia to seek their leverage on Syria and Iran and through them, on Hezbollah's fighters.