Turkey's Foreign Minister has backed calls to unfreeze around £2bn of Libyan cash for humanitarian aid.
Ahmet Davutoglu called for the release of the frozen funds during talks with leaders of the Nato-led coalition in Istanbul, saying that the humanitarian situation was a cause for "grave concern".
"We see merit in the suggestion of the Transitional National Council for the release of $3bn from the frozen assets of Libya under UN supervision," Mr Davutoglu said.
Kuwait and Qatar have already transferred around £60m to the National Transitional Council (TNC) and other countries have also pledged assistance, but rebel officials say they need more cash fast if they are to assume the full obligations of government.
Read more: Turkey recognises Libya rebels
"Countries are starting to look past Gaddafi. He's going to go, and the meeting can be a useful place to take stock of and prepare for that transition," a US official with Mrs Clinton said.
Countries are starting to look past Gaddafi. US official
"That's the way we're thinking about this meeting: trying to see it as a pivot in this process."
The US hopes the talks will strengthen ties with the Benghazi-based TNC - which requested the unlocking of assests - and expand its plans to become more inclusive in hopes of winning stronger diplomatic and financial support.
Delegates from around 40 countries will ask for more details on exactly what the TNC's strategy will be for guiding the country to democratic elections and broadening its political base beyond its strongholds in eastern Libya.
'Action to intensify'
The Foreign Secretary, William Hague, who is also attending the conference, has said that military action against Gaddafi's regime will be intensified.
He said the UN Secretary-General's special envoy to Libya, Abdul Elah Al-Khatib, would be authorised to present terms for Gaddafi to leave power.
"He has taken a central role in this contact group meeting and we see him as the channel for negotiations and for political settlement, while the military pressure on the regime will continue to intensify.
The conference takes place as rebels in Libya's east pulled back after a failed advance on the oil town of Brega.
Brega, a long-held rebel goal, may have been an attempt to strengthen the rebels' position ahead of talks.
Libyan government spokesman Moussa Ibrahim condemned the attack and alleged that Nato is closely coordinating with the rebels in violation of the alliance's UN mandate to protect civilians.
"It was a full scale attack and it was heavy and merciless," Ibrahim said. "We were successful in combating this attack and we did defeat both NATO and the rebels and we killed many rebel forces and captured a good number of them as well."
Meanwhile, Colonel Gaddafi broadcasted a message to a rally of thousands in the western town of al-Ajaylat near the Tunisian border, encouraging loyalists to take up arms to attack the nation's enemies.
"Crashing waves of angry masses, rising to the challenge with high heads and loud voice saying we will never surrender. Smash NATO! We are courageous, we are mujahideen!" said the Libyan leader.