The bomber and the aircraft carrier -- the two mainstays of American defenses for the past 40 years -- will get a new lease on life in the Reagan administration.

Officials say that the White House will include funds for initial production of a new manned bomber and an additional nuclear-powered aircraft carrier next month when it sends amendments to the fiscal 1982 budget submitted to Capitol Hill by the Carter Administration.

Though ne decision has been made on exactly what type of new bomber will be built, officials said it would most likely be a modified version of the B1, the production of which President Carter canceled in a controversial decision of 1977.

Officials said they believe the Air Force could begin deploying sizeable numbers of these new bombers by 1985 and 1986, and that adding these weapons appears to be the quickest and most efficient way to restore some of the balance of nuclear power between Washington and Moscow that the Reagan administration thinks has been eroded in recent years.

The decision to include what are called long lead-time funds for production of a new nuclear-powered aircraft carrier also reverses a Carter administration decision not to seek any money in the fiscal '82 budget for these huge warships. It could mark the start of the kind of major expansion naval leaders have been seeking for years.

Though officials say there is no final acceptance by the Reagan administration as to the ultimate size of the Navy's carrier fleet, a number of officials believe the start on the new carrier will be the first step to a Navy built around 15 carrier task forces permanently deployed in three oceans,

The Navy has 12 carriers in operation plus a 13th that is used for training. The tentative plan is to build two more large carriers, though not necessarily nuclear-powered, in addition to the one in the new budget, over the next 10 years. This would allow, officials say, for permanent U.S. carrier fleets in the Indian Ocean as well as in the Atlantic, Pacific and Mediterranean Sea.

The Navy has maintained a two-carrier task force in the Indian Ocean since late in 1979 when the crises in Iran and Afghanistan developed. But this has caused a severe strain on naval manpower and ship availablity.

Though potential increases in the size of the fleet have seemed unrealistic for some time because the services were failing to recruit and hold the personnel to staff ships, officials say retention has improved substantially in recent months and suggest there may be a slight increase in the size of the Navy and the Marine Corps in the forthcoming Reagan budget amendments.

The decision to move ahead with the new bomber is not surprising. While the Carter administration had no money for it in its last budget, Congress has mandated that the administration present options for a new plane and get one into production by 1987, and has put about $300 million into the budget for research and development work. Officials said they thought the new administration would increase the total spent on the new plane next year -- including the long lead-time hardware -- to between $1.5 billion and $2.5 billion.

Because the new plane probably would be a variation of the B1, officials said the production time can be cut substantially. The idea is that the new bomber eventually would replace the B52s, some of which are 30 years old. The new aircraft, however, gradually would replace the older bombers without losing any of the missions assigned to them.

The new plane, for example, ultimately would be able to penetrate Soviet air defense and fly directly to targets inside Soviet borders. It would also be able to carry conventional bombs and be used as the B52 was in Vietnam. It is also planned to be a more efficient carrier of nuclear-tipped cruise missiles than is the B52.

Thus, as the new plane enters service, it would take on the role that is most difficlut for the B52 -- namely, the problem of flying through Soviet air defenses. The B52s then would be used mostly as cruise-missile carriers that could stand outside Soviet defenses and lob their missiles to targets deep inside the Soviet Union.

Then, as still more of the new planes become available, the remaining B52s would be used primarily in a conventional role. The new plane is meant to carry more cruise missiles than the B52 and to carry them inside its fuselage so that it can fly faster and farther than the B52 in that role. The B52 carries many of its cruise missiles hanging from the wings.

Ultimately, officials believe the United States will build perhaps a minimum of 100 new bombers and possibly a maximum of 150 to 180. The amount will depend on how successful the "stealth" technology is. This new technology is meant to make planes all but invisible to enemy radar by using special materials and designs. But it is not clear yet how soon this technology could be applied to a new warplane.

If progress is rapid in "stealth" technology, then the Air Force might eventually decide to build an even more modern bomber to augment the variant of the B1.