KABUL, Afghanistan — British Prime Minister David Cameron said Tuesday that the progress being made by Afghan forces toward ensuring the country’s security justifies plans to start withdrawing British combat troops.

Cameron said on a visit to the Afghan capital, Kabul, that he’d be making an announcement to lawmakers in London today about “a modest reduction” in Britain’s 9,500-strong force next year.

The prime minister, who has pledged to have all British combat troops out of Afghanistan by 2015, said 426 soldiers will leave this year.

“It’s right to start planning the withdrawal of some of our troops,” Cameron said at a joint news conference with Afghan President Hamid Karzai.

“We’re on track, it can be done and we’re determined to make sure it happens in terms of the time lines we have set out.”

As Cameron talked about prospects for peace, violence was reported across eastern Afghanistan.

The U.S.-led international military coalition said four foreign troops were killed Tuesday – three by a roadside bomb and another in an insurgent attack.

The prime minister said while visiting British troops at Camp Bastion in the southern province of Helmand on Monday that the Afghan conflict is entering a “new phase.”

President Obama pledged June 22 to withdraw 33,000 U.S. soldiers by the end of next year.