The European nations said they're only sending the military advisors to help train and organize Libya's opposition forces as they struggle to loosen Moammar Gadhafi's grip on power. They insist that the officers will not play any role in offensives against Gadhafi's troops.
In Tripoli, Libyan government spokesman Moussa Ibrahim told reporters that foreign troops would be violently opposed if they appeared in major cities.
Cameron also raised the prospect Thursday of a new round of international sanctions, including measures to specifically target Gadhafi's ability to generate revenue from oil sales.
For nearly two months, Gadhafi's forces have attacked Misrata, the only major city still in opposition hands. Hundreds of people have been killed, including British Oscar-nominated war photographer Tim Hetherington and New York-based photographer Chris Hondros.
An aid ship ferried the bodies of the two men out of Misrata on Thursday.
The White House expressed sadness over their deaths and called on Libya to take steps to protect journalists.
The Associated Press contributed to this report.