Prime Minister David Cameron will chair a meeting of the National Security Council later ahead of the strategic defence and security review.
Ministers and officials meet for the third time in three weeks to try to shape the future of the armed forces.
The National Security Council has focused on defence equipment and procurement in recent meetings.
The body is now expected to look at the broader picture as the review enters its final stages.
An announcement on the defence review is expected next week ahead of the Comprehensive Spending Review.
The meeting is intended to bring together the work already done over the past months on the UK's security and defence.
This includes what is needed for counter-terrorism and cyber-security, as well as what kind of conventional military forces the country wants for the future.
BBC defence correspondent Caroline Wyatt says all the indications are that the government is keen for the UK to retain its role on the world stage, as well fulfilling its current commitments in Afghanistan.
That is likely to mean the Army will suffer fewer cuts to manpower than the other services, while the proposed aircraft carriers HMS Queen Elizabeth and HMS Prince of Wales are thought likely to go ahead.
The big question that remains is what kind of financial settlement the Ministry of Defence can hope to get in the current spending review.
As one of the bigger departments, the debate is expected to continue until the last minute.
The hope within the MoD is that the Treasury may be softening its stance, so cuts to defence can be kept below 10%.
The National Security Council meeting is thought to be the last before the strategic defence and security review, although Downing Street said more talks may be necessary.
"I am sure there will be further meetings involving the main actors," the prime minister's spokesman said.