(The opinions expressed here are those of the author, a columnist for Reuters)

LONDON - As Lithuania prepares to host next month's NATO summit, the government in Vilnius knows exactly what it wants - a tripling of German-led NATO forces in the country to deter any Russian ambitions in its direction.

The July 11-12 meeting will give the 74-year-old alliance the chance to showcase a unified response to Russian President Vladimir Putin's invasion of Ukraine. But increasingly public politicking raises the prospect it could highlight divisions.

Any single NATO nation can veto major decisions, with Turkey and Hungary still blocking the accession of once-neutral Sweden, invited to join the alliance in March last year along with Finland.

Swedish accession, NATO officials and diplomats say, should be one of the “jewels in the crown” of the Vilnius summit – but NATO Secretary General Jens Stoltenberg made it clear this week that re-elected Turkish President Tayyip Erdogan has yet to acquiesce.

Also this week, Ukrainian President Volodymyr Zelenskiy – who had been expected to attend as a guest of honour to inaugurate a new stepped-up Ukraine-NATO Council – suggested he might stay away unless the alliance is prepared to offer quicker NATO membership, a move on which members remain even more divided.

Following his trip to China this year, French President Emmanuel Macron appears to now have his own dispute with the alliance, suggesting he opposes a plan to open NATO’s first office in Asia in Japan and arguing that the alliance should remain focused on Europe.

But several Asian and Pacific leaders, including from Japan and South Korea, will attend in Vilnius, suggesting that the alliance will stick with its hawkish line on China.

Behind the scenes, several eastern European states are also lobbying major troop-contributing nations to increase numbers on their soil. An increasingly public competition is also now under way to succeed Stoltenberg, who has made no secret of his desire to return to Norway after nine years in office, but some diplomats suspect he might be persuaded to stick around until a 75th anniversary summit in Washington in April.

Traditionally, NATO likes to have its major public statements and agreements lined up months in advance before a major meeting, with gatherings of defence and foreign ministers several times a year viewed as stepping stones to the summits. While many of those discussions take place behind closed doors, highly public lobbying before a summit appears to be becoming more common.

Barely a week before the Madrid summit last June, Estonian Prime Minister Kaja Kallas tore into alliance military planning to defend the Baltic states in a public briefing in Brussels, warning that existing plans would see her country overrun and the NATO battle groups there defeated if attacked by a force of equivalent size to that Putin threw against Ukraine in February 2022.

NATO'S NEAR-DEATH EXPERIENCE

That intervention helped to deliver impetus for the agreement in Madrid of some of NATO’s most ambitious military plans since the Cold War ended, putting as many as 300,000 alliance troops on a tiered system of alert. Those plans, however, remain publicly ill-defined.

The Vilnius summit would need to go very badly to be worse than that held in Brussels in July 2018, which saw then-U.S. President Donald Trump berate Stoltenberg for several minutes in televised comments before a dinner. That meeting also reportedly saw him suggest the United States might refuse to honour its commitments to defend Europe under Article 5 of the North Atlantic treaty, in which an attack on one member is seen as an attack upon all.

The near-death experience of the Trump era, followed by the Ukraine invasion, has given the alliance something of a new lease of life. Ever since Russia's 2014 annexation of Crimea, the alliance has steadily stepped up its forces and exercises, particularly in Eastern Europe, even if the most exposed nations would like more.

The challenges of delivering consensus in a now 31-member group, however, appear to be growing steadily. The strength of Turkish opposition to expanding the alliance to Sweden and Finland took some by surprise. The intent had been that they joined together, imposing another clear and rapid cost on Russia for its Ukraine invasion.

Instead, Erdogan accused both nations of harbouring and backing separatist Kurdish PKK militants. In Madrid last year, Sweden and Finland signed a deal with Turkey to share intelligence and counterterrorism cooperation and end their respective arms embargoes – but while Turkish officials say Finland has done enough, the Turkish parliament, now joined by its Hungarian counterpart, has repeatedly failed to endorse Sweden.

NATO 'JOLTED AWAKE'

NATO officials hope the end of the Turkish election will make Ankara more pliant. Sweden has now passed a counterterrorism bill, prompting demonstrations this weekend by PKK supporters in Stockholm. At his press conference in Turkey, Stoltenberg stressed that those protests themselves were not “terrorism”, saying that Sweden had now made good on its promises in Madrid.

Turkish officials have expressed further outrage over the burning of a Koran in a right-wing protest in Stockholm earlier this year. Some diplomats at NATO HQ suspect Turkey may be holding out for further concessions both from the alliance and from Washington, including potentially sales of F-16 fighter jets, a freer hand in Syria and maybe even the appointment of a Turk as NATO’s deputy secretary general.

Fixing disagreements over Ukrainian membership may be harder.

In 2008, France and Germany opposed a Bush administration plan to give Ukraine faster membership, a decision many Ukrainians say left the door open for Russia's invasion. Most NATO nations oppose giving Ukraine membership while war still rages, although some Eastern European nations want faster movement.

Last week, Macron, who called the alliance “brain-dead” in 2019 but says it was “jolted awake” by the Ukraine invasion, last week shifted his position, saying the Vilnius summit should give Kyiv a path to membership, and security guarantees until that happens.

Whether other member states shift position remains hard to say.

How well Ukraine’s counteroffensive goes between now and the summit may also shape perceptions – although new Western supplies of tanks and F-16s seem unlikely to reach the front line in time to significantly affect frontline fighting for a while.

That will likely put the Ukraine war into next year – and almost certainly another NATO secretary general. With Estonia’s Kallas seen as too hawkish for some European states, the three most often-touted front-runners appear to be British Defence Secretary Ben Wallace, Canadian Deputy Prime Minister Chrystia Freeland and Danish Prime Minister Mette Frederiksen.

Whoever does get the role will have to handle an alliance that is increasingly challenging to run.

September will see an election in currently pro-NATO Slovakia that could see a more pro-Kremlin right-wing administration come to power.

More importantly, however, next year will bring another U.S. election, with some opinion polls holding out the prospect for Trump's return to power.

* Peter Apps is a Reuters columnist writing on defence and security issues. He joined Reuters in 2003, reporting from southern Africa and Sri Lanka and on global defence issues. He has been a columnist since 2016. He is also the founder of a think tank, the Project for Study of the 21st Century, and, since 2016, has been a Labour Party activist and British Army reservist.

(Editing by Nick Macfie)