While attempting to justify the Arias plan as ''a promising start'' toward peace in Central America, Sol Lino-witz highlights some of the plan's most egregious deficiencies {op-ed, Aug. 16}. As one example, Mr. Linowitz stresses that the Sandinistas must also adopt elements of the more comprehensive draft Contadora treaty (which they have spurned) to satisfy security concerns of the United States and other countries of the region with respect to arms reductions, removal of foreign advisers, etc.

As part of the negotiation process, Mr. Linowitz would also have the United States threaten to send in troops if Soviet bases are established or are in prospect in Nicaragua, or if the Sandinistas attack any of their neighbors. This exigency also lies outside the Arias framework. Jingoistic threats of American force would not be necessary, however, if the Arias plan did not propose a cutoff of aid to the Nicaraguan resistance, which serves as the shield for our security while providing the military leverage needed to promote peace and freedom in Nicaragua.

NICHOLAS D. CAMMERO Fairfax

It seems clear that the Democratic-controlled Congress will seize the Arias plan for Central America as a way to dump the contras. To believe that the Sandinistas will ever agree to democracy, or that the Soviet Union and Cuba will not turn Nicaragua into a military base for a communist takeover of more Latin American countries, is to believe in the Tooth Fairy.

If the Democrats want to stand for the national interest and not justanti-Reaganism, as they seem to, they should join with the president and pass a binding resolution that if the Sandinistas ever 1) allow military bases for the Soviet Union or Cuba, or 2) provide arms for communist takeovers or send their forces across their borders, then the United States will take military action to decisively thwart them.

The Democrats should realize that in so doing they will be committing our "American boys" to combat instead of the contras.

HERBERT W. ROBINSON Bethesda