UNITED NATIONS (AP) _ From his one-bedroom apartment in midtown Manhattan, Zeljko Perovic has begun a campaign to give Montenegro a greater voice at the United Nations, setting up a one-man ``mission'' and getting himself invited to U.N. meetings.

One of two republics that make up what is left of the former Yugoslavia, Montenegro has no independent legal status at the United Nations. Montenegro and Serbia are represented together by Belgrade's U.N. mission.

But with tensions between the two republics increasing _ and heightened last week with constitutional changes that seek to reduce Montenegro's status _ Montenegro is seeking to increase its own diplomatic visibility and garner support for its pro-Western cause.

``We have to protect our interests,'' said Perovic, Montenegro's self-proclaimed ``head of mission and U.N. liaison officer,'' in an interview Friday.

Montenegro is finding support in its campaign from the four former republics that separated from Belgrade in the early 1990s: Slovenia, Croatia, Macedonia and Bosnia-Herzegovina.

On Friday, Slovenia circulated a second letter in three weeks on behalf of Montenegro to the Security Council, enclosing the text of a resolution adopted by the Montenegrin parliament rejecting the constitutional amendments enacted by the Yugoslav federal assembly.

The amendments aim to concentrate power in the hands of Yugoslav President Slobodan Milosevic while reducing Montenegro's status. One paves the way for Milosevic's re-election, the other says parliament's upper house will be chosen by popular vote, curtailing the influence of Montenegro's parliament, which is dominated by Milosevic's opponents.

Slovenia's deputy U.N. ambassador, Samuel Zbogar, said Friday that his government had decided to help Montenegro gain greater visibility at the United Nations because Belgrade wasn't representing its interests here.

That support includes circulating letters to U.N. ambassadors on behalf of Montenegro and inviting Perovic and other Montenegrin officials to the United Nations as ``guests'' of the Slovene mission.

Visitors to the non-public areas of the United Nations must be accredited to the organization or be escorted into the building as a ``guest'' of someone who is.

``They are the democratic light in Yugoslavia and you have to support that,'' Zbogar said in an interview.

Yugoslavia's representative at the United Nations, Vladislav Jovanovic, has bitterly complained about what he calls Slovenia's interference in Yugoslav internal affairs. He has also dismissed Montenegro's quest for official, or even unofficial, recognition at the organization.

``Parts of member states are not entitled to have any official or semi-official mission within the U.N. The appearance of one person claiming to represent Montenegro in the U.N. is totally private business and doesn't have anything to do with the U.N. membership,'' he said in an interview.

Indeed, as a part of Yugoslavia, Montenegro cannot be recognized as an independent U.N. member state. It probably couldn't even get ``observer'' status, which has been granted to entities such as the Palestine Liberation Organization.

In their dispute with Milosevic's regime, Montenegro officials have talked of breaking from Belgrade, but they have stopped short of making a direct move for independence.

Similarly, Montenegro's moves at the United Nations have not been presented as a step toward statehood. But Zbogar and Perovic said they were looking into ways to allow Montenegro to have some type of other accreditation at the United Nations _ or at least be given the same type of access as Belgrade's U.N. representatives.

Belgrade's envoys don't have full rights at the United Nations. In 1992, they were stripped of some membership rights following the independence of four of its six republics. The United States, Britain and the four former Yugoslav republics have demanded that Belgrade apply for membership as a new country.

Belgrade has so far refused, arguing that the independence of its republics didn't affect the ``continuity'' of the country.

Last month, U.S. Ambassador Richard Holbrooke raised Yugoslavia's disputed status as one reason for limiting its access to U.N. meetings. He successfully got the Security Council to block Jovanovic from participating in a council debate on the Balkans, primarily on grounds that Milosevic and other key leaders have been indicted for war crimes.

Montenegro's foreign minister, Branko Lukovac, attended the Security Council debate as a guest of Slovenia, Zbogar said.