David Cameron has announced more money for tackling the threat of roadside bombs in Afghanistan, during his first visit to the country as prime minister.
In a press conference in Kabul, Mr Cameron said the issue of Afghanistan was his "number one priority".
He said an extra £67m would go into countering insurgents' bombs. It is on top of £150m pledged last year by ex- PM Gordon Brown for a similar project.
Mr Cameron later flew to Helmand province to visit UK soldiers.
But he was forced to cancel an earlier visit to a military base because of a security alert.
The PM had earlier said the UK had no plans to commit more troops to the country.
Afghanistan was the UK government's "most important foreign policy" and "national security issue", he said in Kabul.
Britain has about 10,000 troops in Afghanistan, including some 500 special forces.
In response to questions Mr Cameron said the issue of sending more UK troops to the country was "not remotely" on the government's agenda.
Although he did not predict when UK troops would be withdrawn from Afghanistan, he said: "We should all the time be asking 'Can we go further, can we go faster?'
"Nobody wants British troops to be in Afghanistan a moment longer than is necessary."
There has been pressure on the Army to produce more bomb-disposal experts quickly, as a result of the threat of roadside bombs in Afghanistan - the biggest single killer of troops.
Last month the Army's top bomb disposal officer - Colonel Bob Seddon - resigned over fears bomb disposal training could be compromised.
Speaking alongside Mr Karzai at his presidential palace on Thursday, Mr Cameron said the number of British teams dealing with improvised explosive devices (IEDs) would be doubled.
The money is to fund a specialist IEDs team for every sub-unit of the UK deployment in Helmand province, as well as new vehicles, including seven armoured Mastiffs.
The government was committed to countering IEDs, and would also continue work agreed by the previous administration, said an MoD spokesman.
Mr Cameron also said £200m in aid funding would be diverted from existing budgets to help Afghanistan build up its police and civil service capacity, in order to enable it able to handle its own security needs as soon as possible.
That was important in what was "the vital year" to make progress in stabilising the country, he added.
Mr Cameron went on to describe relations between the two countries as "very, very important".
He said: "For me, the issue of Afghanistan is the most important foreign policy issue, the most important national security issue for my country."
Mr Cameron said he would update MPs with a statement to the House of Commons on Monday and that the defence or foreign secretary would give a detailed statement on Afghanistan every three months to keep the public informed about progress.
The PM added: "I think there is progress being made... particularly progress that has been made in terms of driving al Qaeda both out of Afghanistan and... seriously damaging its interests in Pakistan.
"It is through that prism of national security that I want to see this whole issue. Our overriding focus must be to help the Afghans and to help Afghanistan to take control of its own security and its own destiny."
Mr Cameron said that alongside the Nato-led military surge which has been under way for six months, there must be a "proper political settlement".
He said he welcomed last week's Kabul peace meeting - or jirga - at which Mr Karzai discussed proposals to encourage elements of the Taliban to rejoin the political mainstream.
Last month Mr Cameron met Afghan President Hamid Karzai in the UK, and both said they wanted to "further strengthen" relations between their countries.
Since becoming PM he has also sent a ministerial delegation - comprising Foreign Secretary William Hague, Defence Secretary Liam Fox and International Development Secretary Andrew Mitchell - to assess the situation.
Earlier this week, following talks with US Defence Secretary Robert Gates, Dr Fox made clear that he had no plans to switch British forces from Helmand - where the bulk are deployed - to Kandahar where the Americans are preparing a major offensive.
On Thursday the top Nato commander in Afghanistan, General Stanley McChrystal, said the operation to gain control of Kandahar would now move at a slower pace than planned, in order to ensure local support.
This week British soldier Lance Bombardier Mark Chandler, 32, from Nailsworth, Gloucestershire, was killed in a gun battle in Nad Ali district, Helmand.
On Wednesday a soldier from 2nd Battalion The Princess of Wales's Royal Regiment died in an explosion.
His was the 294th UK military death in Afghanistan since 2001. Twenty nine Nato soldiers have been killed this month alone.