WITH THE Rhodesian elections coming up next week, one is struck yet again by the dichotomy that marks American policy toward Israel on the one hand and toward Rhodesia on the other.

The two nations share many common traits. Israel is an island of Jews set in a sea of Arabs, Rhodesia a penisula of whites washed by an ocean of blacks.

Both are regarded by their neighbors as colonial states. While pockets of Jews have lived in the Holy Land since biblical times, the great majority, like the great majority of white Rohdesians, arrived or were born in their new homeland aftrer World War Ii.

Paleestrinian Jews fought gallantly on the Allies' side in World War Ii So did the white Rhodesians. Both states are seeking reconciliation with the majority groups within and around them. Each has shown a capacity to make its own desert bloom.

Yet what is sauce for the Israeli goose never has been gravy for the Rhodesian gander. American policy toward Israel since 1948 has been to strengthen that state militarily and economically by generous grants, low-interest loans and tax credits, U.S. policy toward Rhodesia since 1965 has been to strange it by prohibiting arms sales, eliminating aid and banning trade.

Americans who have served in the Israeli armed forces or worked on kibbutzim have been hailed as heroes. Americans who serve in the Rhodesian armed forces are threatened with loss of citizenship.

The United States and Israel maintain cordial diplomatic relations. The United States refuses to maintain even consular relations with Rhodesia. Israel's American friends are honored; Rhodesia's American friends are characterized as racists.

An Arab who plants a grenade in an Israeli bus is a terrorist. An African who does the same thing in Rhodesia is a freedom-fighter or, at worst, a guerrilla.

The United States accepts Israel's contention it will never negotiate with the gunmen of the PLO. It demands that the gunmen of the so-called Patriotic Front participate in any Rhodesian settlement.

The United states is prepared to under-write and to participate in an observer force to keep the peace between Israelis and Arabs. The administration refuses to send observers even to watch Rhodesia's transition election to black rule.

The United States supports an Israeli-Egyptian peace of which Saudi Arabia, our principal oil supplier, disapproves. The United States insists any Rhodesian settlement must be approved by Zambia and Marxist Mozambique, bordering states of marginal U.S. interest.

None of this is to suggest that U.S. policy toward Israel should be anything other than what it has been. It is to suggest that U.S. policy toward Rhodesia is skewed, counter-productive and will fail.

A cynic might even suggest that in the formulation of policy toward Rhodesia-if not toward Israe-domestic political considerations have been given greater weight than equity or U.S. national interests.