Missile defence was a key Bush campaign pledge.
Following conversations with allies, he is likely to argue that the US cannot be bound by the 1972 Anti-Ballistic Missile Treaty that bans such systems.
Mr Bush may offer to make deep cuts in the US nuclear arsenal in order to placate Russia, which objects to US plans for a missile defence system.
Consultations
He is hoping to speak to Russian President Vladimir Putin just before the speech at the Pentagon's National Defense University, at 1430 local time (1830GMT).
The venue is the same one that former President Bill Clinton used to announce eight months ago that he did not think technology was sufficiently advanced to commit to NMD.
Missile defence was a key Bush campaign pledge.
Mr Bush believes that "the greatest nuclear threat or missile threat comes from rogue nations, accidental launches, [or] launches of small or single missiles", his spokesman Ari Fleischer said.
In addition to Russia's objections, China fiercely opposes the programme, and even many US allies have reservations about it.
On Monday morning, he spoke to the leaders of France, Germany, Canada and the UK about the plan, as well as to Nato Secretary-General Lord Robertson.
But Mr Bush will not let allies' objections stand in the way of US plans, Mr Fleischer said.
"He views it as a question of leadership. He believes that if the US leads and that we consult wisely, our allies and friends will find good reason to follow and join with us," he said.
Mr Bush is not expected to announce timetables or budgets in the speech on Tuesday.
Arms reduction
He may offer to make significant cuts in the US arsenal of roughly 7,200 nuclear weapons, perhaps reducing it to less than the 2,000 to 2,500 Washington and Moscow discussed in Start III negotiations.
Such a move may help placate Russia, but would not necessarily satisfy China, which has a much smaller arsenal than Washington or Moscow.
Beijing is worried that the technology could be used to defend Taiwan, which China considers to be a renegade province.
China and the US have exchanged angry words over Washington's commitment to defending Taiwan in case of Chinese attack.
China has threatened to increase its nuclear arsenal in response to US attempts to deploy NMD.