UNITED NATIONS -- U.S. relations with Russia have become only more complicated with the appointment of special counsel Robert Mueller to look into Moscow's alleged ties with the Trump administration -- allegations focused, in part, around meetings held with Russia's Ambassador to the U.S., Sergey Kislyak.

Now it appears that Vladimir Putin is setting his sights on the United Nations. Diplomats and counterterrorism experts say Russia is reshuffling its diplomats, making new appointments and proposing to move Kislyak or another top Russian official to U.N. headquarters in New York, and one of those officials is expected to run a new U.N. counterterrorism office.

Before that happens -- if it does -- the Russians will have other vacancies to fill as a priority. For starters, there has been no Russian Ambassador at the U.N. since the sudden death in February of Vitaly Churkin.

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On Thursday, Russian Deputy Foreign Minister Gennady Gatilov nominated Deputy Foreign Minister Vasily Nebenzya to the position. Confirmation of the nomination by Russian lawmakers is still pending, but Nebenzya has served in New York previously and headed the foreign ministry's human rights division.

Also, to relieve the embattled Kislyak in Washington, Moscow is reportedly preparing another Deputy Foreign Minister, Anatoly Antonov, to head to the U.S. capital.

The real intrigue, however, is around the U.N.'s soon-to-be unveiled office of counterterrorism, a flagship program of the new U.N. Secretary-General Antonio Guterres.

"In short, I have asked the entire U.N. system to 'act as one U.N.' on what I consider one of the greatest challenges of our time," Guterres said about his initiative in a message delivered in Moscow last year. The timing of the inception of the U.N.'s first new office in decades -- and the appointment of its leader -- could not be more delicate.

Jeffrey Feltman, U.N. Under-Secretary-General of Political Affairs and a former U.S. foreign service officer, tells CBS News that the General Assembly's advisory office on administration affairs (ACABQ) this week recommended approval of the new office, sending it to the committee to negotiate a budget. The next step is for the General Assembly to approve the new office, including the appointment of a new Under-Secretary-General to head it, which it is widely expected to do.

The new official "will be appointed by the Secretary-General with the consent of the 193-nation body because it's a General Assembly mandate," Mattias Sundholm, Communications Adviser at the U.N. Counter-Terrorism Committee Executive Directorate, said. In U.N. terms, that means that the Security Council does not have formal approval power -- or the ability to block the appointment.

In an unwritten agreement crafted last fall Russia agreed to forgo its regional turn in the selection of the next Secretary-General in exchange for the appointment of a Russian official to lead the new office, multiple sources tell CBS News.

"That was the deal," a Security Council diplomat from one of the five permanent member states (Russia, U.S., China, France and Britain) told CBS News. In total, diplomats from eight of the 15 Security Council member states confirmed the quid-pro-quo agreement to CBS News, including officials from all five permanent members.

"This is not a Security Council mandate, this is up to the General Assembly," a U.S. official familiar with the negotiations told CBS News, "and it is not something that we feel we have to nix." Other diplomats confirmed that the U.S., at this point, is not inclined to try and block a Russian official from leading the new U.N. office.



Feltman explained that existing U.N. counterterrorism programs (known by their acronyms CTED and CTC) which report to the Security Council will remain intact, but two other counterterrorism offices will be moved under the new umbrella office of counterterrorism, once it's approved by the General Assembly.

In mid-May, U.S. Deputy Ambassador Michele Sison told the Security Council that the Council can work closely with the new U.N. office of counterterrorism, which, when established, "will coordinate CT efforts across 38 UN offices."

During a trip to Russia in April for the Moscow Conference on International Security, Feltman said the new office would, "increase our impact on the ground."

That is where Russia comes in.

Two Russian candidates appear to be in the running for the new gig as U.N. counterterrorism czar: Kislyak and Andrey Krutskikh, a senior advisor to the Kremlin and a cybersecurity expert. If Kislyak is hopelessly embroiled in the D.C. investigations when the new U.N. office is announced, Russia may turn to Krutskikh.

Krutskikh has been at the forefront of Russia's strategies of information warfare, reported extensively by David Ignatius of the Washington Post earlier this year.

While the Kremlin has not confirmed any of the pending appointments, the Russian press has. Russia's business daily Kommersant and state-run news agency RIA Novosti both reported this week that Antonov was to replace Kislyak in D.C., most likely, in July after a possible meeting between Putin and President Trump on the margins of the G20 summit in Hamburg.

Howard Stoffer, Associate Professor of National Security at the University of New Haven, who served in the U.S. Foreign Service and as deputy director of an existing U.N. counterterrorism committee, says the new office proposed by Guterres should be a good place to develop a global strategy for pooling information and countering violent extremism.

The U.N. diplomats who spoke to CBS News were reluctant to voice any concerns they may have about the prospect of Russia heading up a new office on counterterrorism.

But human rights groups and U.N. analysts -- even those who acknowledge the need for a more cohesive U.N. counterterrorism strategy -- have understandable concerns.

Richard Gowan, senior policy fellow at the European Council on Foreign Relations, agrees that streamlining is needed: "Consolidating and rationalizing the elements of the U.N. dealing with counterterrorism makes sense. They have always been a little fragmented."

But he adds there have been "recurrent concerns that Guterres made a specific political commitment to Moscow that a Russian official would be the U.N. terror tsar."

Matthew C. Waxman, the faculty chair of the Program on Law and National Security at Columbia Law School, doesn't see the still-unfurling investigations in Washington D.C., focused on Moscow's election interference and alleged Trump campaign ties, "as so key here."

"A problem with working any global issue through the U.N. is that it requires reaching agreement with partners we might not otherwise choose," explains Waxman, who served in the Departments of Defense and State during the administration of George W. Bush.

The bigger issue, he says, is that President Trump, "has signalled that he wants to work more closely with Russia on counterterrorism, and it's true that Russia itself faces threats from some Islamist terror groups, but U.S. and Russian interests and approaches on this issue are far apart. In Syria, for example, Russia has shown more interest in supporting Assad than combating ISIS."

"In general," Waxman says, "Russia embraces tactics that run counter to our values and strategy."

Filed by CBS News foreign affairs analyst Pamela Falk, at United Nations Headquarters.