Interior Secretary James G. Watt said yesterday it could take more than a year to develop a political "consensus" on the placement of a flag and statue at the Vietnam Veterans Memorial on the Mall.

"It's a memorial and a monument to those who lived and died for America, and it's a political expression," Watt told the U.S. Chamber of Commerce. "It's not an expression of just the arts community, although it includes them, and so I would expect that the matter will be resolved within the next 12 to 15 months. I'd like to see the consensus come along."

An Interior Department spokesman said later that Watt does not plan to submit a proposal for the flag and statue placement for approval by the Commission of Fine Arts at its Feb. 8 meeting. Because the commission must approve any plan, Watt's decision not to make the submission stalls the approval process indefinitely.

Jan C. Scruggs, head of the Vietnam Veterans Memorial Fund, the group that raised private money and obtained congressional approval to build the memorial, yesterday called Watt's position "shocking."

"We have steadfastly adhered to keeping the Vietnam Veterans Memorial unpolitical, and to see Secretary Watt injecting politics into the memorial is very distressing," Scruggs said. ". . . I don't think Secretary Watt is handling it in the best interests of Vietnam veterans or our nation."

Watt's unexpected decision comes amidst pressure from some Vietnam veterans who dislike the plan, tentatively approved in an earlier Fine Arts Commission meeting, to place the flag and statue in an "entryway" arrangement some distance from the polished black granite walls of the memorial.

The "entryway"--a plaza with the American flag, the statue of three soldiers by Washington sculptor Frederick Hart, and indexes lists to help visitors find the names of the memorialized fallen soldiers--would be located near a grove of trees about halfway between the Vietnam Memorial and the nearby Lincoln Memorial.

"The guarantee that we had was that it would all work together as one memorial," said James Webb, a best-selling author who has opposed the "entryway" concept in favor of having the flag placed near the apex of the "V" shape of the memorial and the statue placed directly in front of it.

The Fine Arts Commission, headed by J. Carter Brown, had opposed this on esthetic grounds. "Everybody agreed to it except the Fine Arts Commission," Watt said yesterday.

Scruggs' position is that any of three plans--including the entryway one, the one Webb likes, and another generated by the American Institute of Architects--would be fine as long as the decision is made quickly and the matter put to rest.

The memorial was dedicated last November in a National Salute to Vietnam Veterans organized by Scruggs' group and attended by an estimated 150,000 persons from across the country. The addition of an American flag and figurative statue was agreed on to placate those who disliked the memorial design by Maya Ying Lin. All that remains now is to figure out where to place them.

"What's been the biggest problem all along is those guys Scruggs and others have been in a hurry to throw something together," said Webb. ". . . There's been very little historical context in their thinking, historical or metaphysical." Webb and some others think the Maya Ying Lin design is a negative ideological statement that dishonors Vietnam veterans.

But the mainline national veterans organizations supported the memorial--and its design--and yesterday spokesmen for some of them expressed surprise at the continuing squabble in Washington.

"There are actually three proposals sitting on Watt's desk right now . . . We find all of them acceptable," said Bob Ashworth, national programs director for AMVETS, which has 200,000 members representing all of America's wars. "As far as we're concerned, he's delaying . . . He's got some funny ideas about this memorial . . . The memorial's up. Why can't they just locate the statue and the flagpole?"

American Legion National Adjutant Bob Spanogle said the legion's position is that the flag and statue must be "prominently placed . . . It's pretty sad that there are 58,000 names of American troops who died in Vietnam on that memorial and we're still arguing about this. Unbelievable!"

Cooper T. Holt, executive director of the Veterans of Foreign Wars, which claims more Vietnam veteran members than any other veterans organization, sent a letter to Watt early this week saying he should send all three proposals on his desk to the Fine Arts Commission and adding that the VFW "is willing to accept whichever proposal, if any, the commission . . . approves . . . Further delay . . . threatens to destroy all that has been achieved."