Rhodesia's "window on Rhodesia for the American people," as Kenneth H. Towsey always liked to describe his lobbying office, seems about to close.

That is, as Towsey sees it, unless an American financial angel turns up quickly to pick the financial tab that has been in the range of about $150,000 a year for the Rhodesian Information Office in Washington.

But as official at the Treasury Department's Office of Foreign Assets Control see it, pending further legal study, the Rhodesian "window" is going to close, period.

The UN Security Council voted unanimously last Friday for a resolution to block "the use or transfer of any funds in their territories by the illegal regime in Southern Rhodesia . . ." The target of this latest squeeze on Rhodesia's white-ruled government was Rhodesian information offices in Washington, Australia and South Africa.

Towsey already has issued what he ruefully describes as a "kind of valedictory" for the office at 2852 McGill Terrace NW, where he has operated as a diplomat-in-limbo since 1966.

The U.N. resolution "chops off Rhodesian resources" for his small operation. Towsey acknowledged yesterday.

But, he said, ?It does not, as I understand it, preclude the possibility of something being done out of local sources . . . I really haven't got very far into that."

Neither has the Treasury Department, the action agency for the United States which joined in sponsoring the U.N. cutoff resolution, an official there said yesterday.

However, the Treasury official said, "I think it would prohibit" the use of funds from any source for the Rhodesian office here, as long as they are an agency of the Rhodesian regime." Under the language of the U.N. resolution, he said, it appears that "the ssource would not be relevant."

As soon as it is decided whether or not an executive order form the President is needed to carry out the U.N. resolution, the official said, instructions will go out to banks to block the use of funds for the office.

Towsey, 57, came to Washington in 1964 as a counselor for Rhodesian affairs in the British embassy. When fairs in the British embassy. When Rhodesia in 1965 unilaterally declared its independence from Britain, Towsey and Henry J.C. hooper set up the Rhodesian Information Office, which has three local secretarial employees.

It has operated under the Foreign agents Registration Act.

When the United States in 1970 cut its remaining diplomatic link to Rhodesia by closing its consulate in Salisbury, Rhodesia's capital, Towsey still retained the friendship of such influential senators as James O. Eastland (D-Miss.) and Barry M. Goldwater (R-Ariz.) and numerous House members. But since the Carter administration's accelerated championship of black majority rule in Africa, the doors and windows have been closing rapidly.

Towsey, in his official "valedictory," wryly said that "when the Rhodesian government is cooperating fully with an Anglo-American initiative designed to resolve the (racial) conflict in Rhodesia .. . this is a time for more communication, not less."