Hundreds more British troops will be sent to Afghanistan during the coming year to help to improve protection for British Forces, Gordon Brown announced yesterday after talks with President Bush.

Despite warnings of “overstretch” in the Army, the Prime Minister said that levels of British Forces would reach their highest point.

As the bodies of the latest five soldiers to be killed in Afghanistan were returned, ministers said that the extra troops, sent as part of a “reconfiguration” of the British contingent, would improve security for British servicemen and women.

At the same time Mr Brown heralded tougher sanctions against Iran as he and Mr Bush presented a strong united front against terrorism.

Speaking at a joint press conference, Mr Brown previewed a later Commons announcement by his Defence Secretary that the total number of British personnel would increase from 7,800 at present to about 8,030 by next spring. But the Prime Minister made plain that it would not be done by transferring British Forces from Iraq. “You cannot trade numbers between the two countries,” he said.

Mr Brown also surprised the Americans by announcing the immediate intention of Europe to freeze the assets of the Melli Bank Iran, and promising action on a new phase of oil and gas sanctions, which is opposed by several countries. His words gave the impression that the bank sanctions would come into immediate effect. In fact “technical steps” have to be taken before the sanctions are implemented, probably next weekend, the Foreign and Commonwealth Office said. The fact that formal approval has yet to be sealed for further sanctions led to speculation that Mr Brown had jumped the gun with his announcement to coincide with the President’s visit.

Des Browne, the Defence Secretary, told MPs that, because of reorganisation and “the changed nature of the tactical situation”, 400 posts would be removed from Afghanistan and replaced with 630, creating a net increase of 230 personnel.

The additional troops, as well as helping to improve protection for British personnel, would increase training and mentoring for Afghan security services and assist reconstruction and development. It is understood that extra specialist personnel, such as engineers and logistics staff, would be sent in the next few weeks.

Britain’s force of Harrier jets was to be replaced next spring by an equivalent force of Tornados, he said. Extra helicopter crews would be among the deployments.Mr Browne said that there had been improvements in security, but the Taleban had switched from insurgency to terrorist tactics — including suicide bombers recruited from “vulnerable” communities.

But, he said, despite setbacks such as the recent escape of Taleban fighters from a Kandahar prison “our view is that the Taleban are losing the fight in southern Afghanistan”.

Mr Browne said that the new deployments included soldiers to man extra Viking and Mastiff vehicles, more specialists for reconnaissance and warning systems in Helmand and reinforcements at the Royal Air Force Regiment Squadron at Kandahar airbase. He added that, when 3 Commando Brigade was deployed in October, it would have an additional infantry battalion headquarters and there would be an extra troop of Royal Engineers to assist with projects to support local communities.

The Prime Minister had said earlier: “We have resolved, first of all, as we did some years ago, that it is in the British national interest to confront the Taleban in Afghanistan, or Afghanistan would come to us.”

But he said it was not a question of moving British troops from Iraq to Afghanistan, as there was a job to do in both. He said that President Bush was “a true friend of Britain” and thanked him for “the importance he attaches to enhancing our transatlantic partnership from the work we do in Afghanistan and Iraq to every part of the world”.

Mr Brown said their message to the Iranian people was that they did not have to choose a “path of confrontation” with the West, and Britain wanted to do everything possible to maintain dialogue with Tehran. “But we are also clear that if Iran continues to ignore resolutions, to ignore our offers of partnership, we have no choice but to intensify sanctions.” He said that Britain would urge Europe to impose further sanctions on Iran, including freezing the overseas assets of Iran’s biggest bank and new sanctions would start on oil and gas.

President Bush praised Mr Brown for the “steadfastness and resolution that he had shown in rooting out terrorism in all parts of the world”. Speaking about the Iraq war, he said he was “absolutely confident that the decision to remove Saddam Hussein was the right decision”.

Within hours of the press conference, Mr Bush’s aides cast doubt on the speed of the Iran sanctions. Stephen Hadley, the President’s National Security Adviser, said that further action on oil and gas supplies “would be very much significant to the Iranian regime”.

Some US officials are sceptical about the latter suggestion, not least because it could prompt Iran to create further turmoil in the fragile global energy market. “They are complicated — oil and gas sanctions — and Prime Minister Brown has thought we need to put them on the agenda,” Mr Hadley said.

The European leadership is also significantly more cautious than Britain about further measures, with the summit last week between the European Union and US producing an opaque statement, which White House officials suspect could mean merely implementing previous sanctions agreed by the UN Security Council.

Angela Merkel, the German Chancellor, has promised to put more pressure on her country’s business community to sever economic ties with Iran, worth billions of dollars. But last week she emphasised that new sanctions would be most effective if they were agreed by the Security Council — an argument which diplomats regard as code for delay.

Bank Melli Iran (Iran National Bank) has been reported to have moved assets from the European banks, fearing that sanctions would affect its access to investments.

This has been denied by the bank’s London branch, which said: “It should be noted that BMI continues to maintain very significant assets and investments in the EU and has every intention of doing so in the future.”

President Bush and his wife later visited Roman Catholic and Protestant children at a primary school in Belfast in a symbolic endorsement of the peace process.

After meeting Northern Ireland’s power-sharing Executive at Stormont Castle, Mr Bush held up the Province as a template for solving conflicts and urged US businesses to invest there. He thanked Peter Robinson, the First Minister, and his deputy, Martin McGuinness, for hosting meetings between Iraqi factions in Belfast, observing that the collaboration of the two men would have been unimaginable ten years ago.

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