Boris Johnson is set to hold talks with military leaders as he aims to get the armed forces "match fit".
The Prime Minister was set to meet Chief of Defence Staff Sir Nick Carter plus the heads of the Army, Royal Navy and Royal Air Force, among others, to discuss plans for the armed forces.
It comes after Mr Johnson hosted serving military personnel at Downing Street on Wednesday evening.
His talks with British military chiefs and Defence Secretary Ben Wallace on Thursday take place after Chancellor Sajid Javid announced £2.2 billion extra for the Ministry of Defence at the spending round earlier this month.
MPs have repeatedly pressed the Government to increase defence spending, with concerns also raised over personnel numbers and equipment.
Mr Johnson said: "As the world becomes a more competitive and challenging place, maintaining a world-class armed forces is as important as ever.
"Defence has a vital role to play in supporting global Britain's role in the world. It underpins the strength of our alliances and enables us to support the rules-based order in a time of international uncertainty.
"I look forward to speaking to the service chiefs today about how we invest and modernise our armed forces - getting them 'match fit' for the global security challenges that lie ahead."
Mr Johnson also confirmed the next Nato leaders meeting will take place in Watford on December at the Grove hotel.
On the Nato leaders meeting, Mr Johnson also said: "The UK will continue to play a leading role in strengthening the alliance with our armed forces are at the forefront of that effort and I'm pleased that we will be hosting the next meeting of Nato leaders in Hertfordshire, marking 70 years of this vital alliance."
