Nato Secretary General Anders Fogh Rasmussen has said he was "confident" that the UK will fully live up to its military commitments to the alliance despite cuts in defence spending.
Mr Rasmussen was speaking after a visit to 10 Downing Street, where he held talks with David Cameron about the new strategic concept which Nato aims to agree at the Lisbon summit later this month and briefed the National Security Council on progress in Afghanistan.
He said that the Nato-led international troops were putting the Taliban under pressure throughout Afghanistan which could help drive the insurgents to the negotiating table.
"Right now, we are seeing progress in Afghanistan," Mr Rasmussen told reporters outside Number 10. "The Taliban is under pressure everywhere. We are now attacking the Taliban strongholds in the south, in Helmand and Kandahar, and we see progress.
"Actually, I do believe that this military pressure on the Taliban is the best way to ensure that they will also seek a political solution to the conflict."
Mr Rasmussen said he "warmly welcomed" this week's announcement of a defence co-operation pact between the UK and France, which he described as "an excellent example of how we can strengthen our defence, even during a period of budgetary restraint".
George Osborne's spending review last month sliced 7.5% off Ministry of Defence budgets over the coming four years, with the loss of jets, tankers and airbases and projected manpower reductions of 7,000 soldiers, 5,000 sailors and 5,000 airmen.
But Mr Rasmussen said: "I feel confident that the UK will be able to fulfil her commitments within our alliance. The UK will stay committed to our international operations, like the one in Afghanistan, and I would also remind you that the UK is still one of the allies that fulfil the Nato target to spend at least 2% of GDP on defence.
"Of course, the Prime Minister and I have discussed this issue and I feel confident that the UK will fully live up to her commitments."
Mr Rasmussen said that the new strategic concept, launched last year and set to be agreed in Lisbon on November 19-20, would make Nato "more effective, more engaged, more efficient".