Coalition troops are increasingly falling victim to roadside bombs
US President George W Bush has said more US troops will be deployed in Afghanistan by next year.
Mr Bush said June had been a "tough month" - it was the deadliest month for foreign troops in Afghanistan since the 2001 fall of the Taleban.
Records show at least 45 foreign soldiers died in fighting or accidents.
They were serving either with the Nato-led International Security Assistance Force (Isaf) or the US-led coalition in the country.
There are currently about 60,000 foreign soldiers in Afghanistan - most of them are part of Isaf.
The troops include about 33,000 US soldiers and some 28,000 Nato forces from 40 countries.
"We're constantly reviewing troop needs, troop levels. We're halfway through 2008... We're going to increase troops by 2009," Mr Bush told reporters in Washington.
"One thing, however, that you got to understand is that we have doubled Afghan troops - coalition troops have doubled from two years ago."
Mr Bush conceded that June had been a "tough month in Afghanistan".
Of the soldiers killed, 28 were American - the highest monthly toll since US-led troops ousted the Taleban in 2001.
"But it's also been a tough month for the Taleban. You know, one reason why there have been more deaths is because our troops are taking the fight to a tough enemy, an enemy who doesn't like our presence there because they don't like the idea of America denying safe haven," Mr Bush said.
Mr Bush said it had also been a "tough month" for the Taleban
On Tuesday, British Prime Minister Gordon Brown urged all Nato countries involved in the war in Afghanistan to make "their fullest possible contribution".
More than 40% of the 122 foreign soldiers who have died in Afghanistan during 2008 were killed in June, according to official figures collated by the independent website icasualties.org.
Most were killed by roadside bombs hitting their convoys or patrols.
Isaf says that the high casualty figures should be seen in the context of a higher number of international troops fighting the Taleban.
The icasualties website says that 31 soldiers - including 29 Americans - were killed in Iraq in June although there are twice as many troops there as in Afghanistan.
Last month, a Pentagon report predicted that a resurgent Taleban was likely to step up the scope of its attacks during 2008.
The month of June also saw the international community meet in Paris to pledge about $20bn (£10bn) to rebuild Afghanistan - while at the same time demanding that more efforts are made to stamp out corruption and co-ordinate relief efforts.