The panel said extra troops were required so the Canadian forces can focus on training Afghan forces.
"We accept the analysis that for this mission to go forward, achieve its objectives and be successful," Harper said.
"We do have the need for a substantial increase in combat troops, and particular needs in terms of military equipment."
"Both of those recommendations have to be fulfilled or Canada will not proceed with the mission in Afghanistan."
The panel had also recommended Canada purchase helicopters and unmanned aerial reconnaissance vehicles.
Withdrawal pressure
Harper's Conservative administration is under pressure to withdraw its 2,500 troops from Kandahar, a former Taliban stronghold, after the deaths of 78 soldiers and a diplomat.
The mission is set to expire in 2009 unless Canadian politicians approve an extension.
Harper said he had already spoken to Stephane Dion, the leader of the main opposition Liberal Party, and would ask parliament to approve the conditions for the Canada's continued presence in Afghanistan.
Nato has struggled to convince member states to send more troops to dangerous parts of Afghanistan.
Britain, Canada, the Netherlands and others, alongside the US, have borne the brunt of a resurgent Taliban campaign of violent attacks.
The US contributes one-third of Nato's 42,000-strong International Security Assistance Force mission, making it the largest participant, on top of the 12,000 to 13,000 American troops operating independently.