President Carter told a group of out-of-town editors here that the United States does not have enough military strength to protect the critically important Persian Gulf region without the aid of allies and the local nations that feel threatened.

The president's acknowledgement of this situation Tuesday represented a slight yet potentially significant change in tone from his State of the Union address to the nation last week.

At that time, the president talked at one point about the situation in the region demanding "collective efforts." But the key paragraph that drew world attention was his effort to let "our" position be perfectly clear. An attempt by any outside force to gain control, he said, "will be repelled by use of any means necessary, including military force."

He told the editors the United States can protect its interests in the region. "But I don't think it would be accurate for me to claim that at this time, or in the future, we expect to have enough military strength and enough military presence there to defend the region unilaterally" without the kind of cooperation about which he had previously spoken.

Meanwhile, in developments yesterday, the senior State Department expert on Soviet affairs, Marshall Shulman, told a House Foreign Affairs subcommittee that the Kremlin has probably begun drawing troops for the first time from Soviet Warsaw Pact divisions in East Germany to helf fill the ranks in Afghanistan.

Shulman said Soviet troop strength in Afghanistan appears to have grown in recent days from 85,000 to about 92,000, involving six divisions.

He said the Afghanistan rebels fighting the Soviets now are fairly heavily armed with Soviet weapons received from Afghan army deserters.

Aid from outside the region that may be reaching the rebels, he said, was not very significant. Asked later if the United States was aiding the rebels, he would say only that the matter was being discussed.