IN THE midst of an enviably quick transition of leadership from Tony Blair to Gordon Brown, the British people saw their country’s terrorist threat level raised to critical, after back-to-back attempts to inflict massive destruction with car bombs. As a result they, and we, were handed a fresh reminder of how little counterterrorism has to do with conventional war-fighting.

This is not a lesson the new prime minister appears to need. Brown has long been committed to disengaging his country from its involvement in America’s disastrous war in Iraq. But he also has been promising a comprehensive review of all his government’s tools for combating terrorism — “all the means at our disposal: military, security, intelligence, economic, and culture.”

This review should not be merely an abstract discussion. The nature of a government’s antiterrorism strategy is expressed in the way it spends the money available to protect its citizens.

As finance minister, Brown’s experience in counterterrorism has mostly involved cutting off funds to terrorist groups. But his path to the top job has also made clear to him the importance of the way security budgets are put together. In October he promised that in the course of reviewing overall spending during the coming year he would be considering “the case for a single security budget, an annual updated statement setting out the country’s national security strategy.”

Why does this matter? Over here, the Bush administration’s national security strategy officially embraces a “comprehensive” approach, including all the military and non military tools on Brown’s list. But without a single security budget bringing spending levels for each of them together in one place, the relative balance among them is obscured. And the debate over this balance — the right apportionment of resources to make us safer — never really happens.

That is why we convene a group of security experts every year to produce a mock-up of what we argue our government should be providing: “A Unified Security Budget for the United States.” We bring all the categories of security spending in the president’s budget request together in one budget. This exercise shows that in fiscal 2008, 90 percent of all our foreign policy and security resources are allocated to the military; 6 percent are devoted to homeland security; 4 percent go to the tools of conflict prevention, including diplomacy, foreign aid, peacekeeping, and nuclear nonproliferation.

A single security budget would enable consideration of security trade-offs like the following: the F-22 fighter jet, one of the most troubled and strategically questionable programs in the US arsenal, is set to receive a $600 million increase in the president’s budget. Forgoing this increase could permit any of these alternatives: tripling the amount budgeted to cancel the debt that is crippling development in the world’s poorest countries; increasing US contributions to international peacekeeping operations by 50 percent; tripling the amount allocated in fiscal 2007 for domestic rail and transit security programs.

Or how about this: Canceling the administration’s initiative to build offensive space-weapons, which threatens to create a whole new arms race, could provide the $800 million needed to double the originally requested annual budget for the State Department’s Office of Reconstruction and Stabilization. This corps of civilian experts in post-conflict rebuilding, envisioned for Iraq and other locations such as Haiti and Sudan, has been an unfunded political football since it was proposed in 2003. The Pentagon supports it. “If you don’t fund this, put more money in the defense budget for ammunition — because I’m going to need it,” one Marine general recently said.

Prime Minister Brown will soon be sitting down with his country’s closest ally. Since it is clear that he has some ideas about that relationship that differ from his predecessor, their conversations should be interesting. Surely they will allot some time to sharing their respective conceptions of what a “comprehensive” approach to security means. Brown needs to make clear that without the grounding of a unified security budget, it means much less.