Warsaw, Poland - John Bolton, the hardline US national security adviser, undertook a regional tour of countries that Russia considers within its traditional sphere of influence.
Eastern Europe "is seen as a buffer zone both between Russia and Western Europe, as well as between China and Europe, to which the region is a gateway", Michał Romanowski, security expert at the German Marshall Fund in Warsaw, told Al Jazeera.
In Ukraine and Moldova, elections ushered in new pro-Western governments earlier this year, which the United States sees as allies in its geopolitical tug of war. With Belarus increasingly wary of the Kremlin's expansionist ambitions, the US is seeking to offer economic and security incentives to draw Belarus to the West.
"The region has been integrated into a contest between global powers, but in a way which could ultimately benefit it," added Romanowski.
As the first senior US official to visit Ukraine since President Volodymyr Zelensky's ascent to power in May, Bolton used the trip to caution against being pulled into China's sphere of influence by "debt diplomacy".
Bolton's visit comes at a time when the US is locked in a trade war with China and worried about Beijing's expanding global influence.
Bolton expressed concern over a pending deal to sell Ukrainian aircraft engine-maker Motor Sich to China.
"We laid out our concerns about ... unfair Chinese trade practices, threats to national security that we've seen in the United States," he said in Kiev.
In Moldova, Bolton held talks with recently elected Prime Minister Maia Sandu, who heads the pro-Western ACUM (Now) party. He also met President Igor Dodon of the Russia-leaning Socialist party.
Since assuming office in June, Sandu has tried to strike a delicate balance between the European Union and Russia, on which the country depends for energy. She is also hoping to tighten security ties with the US, which supports the modernisation of Moldova's defence sector to the tune of $15m annually.
Bolton reaffirmed the importance of Moldova's "sovereignty and independence", mentioning its frozen conflict with the breakaway parastate of Transnistria, which is backed by Moscow.
"There are real [security] challenges in the region and outside the region. The United States believes very strongly in the sovereignty and independence of Moldova. It's up to its citizens to decide what its future will be, not to outside influences," said Bolton.
Snub to Putin
Bolton praised the government's anti-corruption efforts, hinting they would be a prerequisite to attract American investment, which Moldova seeks for its energy, infrastructure and transport sectors.
"I'm expressing best wishes for your anti-corruption campaign, which is extremely important for potential US investors and business partners, because they believe in a strong rule-of-law system, to have government agencies that are accountable, and a corruption-free environment," said Bolton.
The president of Belarus is beginning to display more independence. Therefore America has decided that through its politics it can encourage greater autonomy.
Professor Longin Pastusiak
The ostensible goal of the visit was "to strengthen the pro-democratic, pro-European leg of the coalition, which only recently seized power and it remains unclear how long it will hold onto it", said Wojciech Kononczuk, head of the department for Ukraine, Belarus and Moldova at the Centre for Eastern Studies.
In Belarus, Bolton met President Alexander Lukashenko, who has been in power a quarter of a century, acquiring the moniker "Europe's last dictator".
After the West imposed sanctions on Belarus, the two countries severed diplomatic relations in 2008. Bolton's trip marks the highest-level US official to visit the country in almost two decades.
Spooked by Russia's invasion of Eastern Ukraine and its renewed interest in closer union with Belarus, Lukashenko has sought an opening with the West. Earlier this year, Belarus scrapped the cap on the number of American diplomats allowed in the country.
"The president of Belarus is beginning to display more independence. Therefore, America has decided that through its politics it can encourage greater autonomy," said Professor Longin Pastusiak, a historian and former vice president of the NATO parliamentary assembly, told Al Jazeera.
Bolton used the visit to snub Putin. Addressing Minsk's relations with Moscow, he said: "What the people of Belarus want really should determine what their relationship with Russia is."
Bolton concluded "there are significant issues in the bilateral relationship involving human rights and nonproliferation", but urged dialogue "where Belarus's interests and the interests of the United States coincide".
Kononczuk was more sceptical. He told Al Jazeera at a time of strained relations with Russia, Lukashenko could be showing his neighbour that "if they do not get along, he can play another piano".
"But I think that is a simplification and that there really is no other piano to play in Belarus's foreign policy," he added, implying that Lukashenko's actions had been coordinated with Moscow and the meeting was merely symbolic.
Such US advances on Russia's periphery have upset Moscow in the past, such as when Bolton brought up weapons sales to Armenia during his tour of the Caucasus last year.
To polish off the tour, Bolton agreed with Poland's defence minister Mariusz Błaszczak on Friday on six locations for the additional 1,000 US troops to be stationed on Polish soil, according to a deal struck in June.
"Poland has been an outstanding partner of the US and NATO, spending more than two percent of GDP on defence," said Bolton in Warsaw.
Kononczuk concluded the meetings were unprecedented. "Never before have the heads of defence in these three countries, Poland, Belarus and Ukraine, been visited by their American counterpart. It is also likely to not have been the last meeting," he said.
The talks come just weeks after the US formally withdrew from the Intermediate-Range Nuclear Forces (INF) Treaty on August 2.
Vice President Michael Pence stood in for President Donald Trump at the commemorations of the 80th anniversary of the start of World War II in Warsaw on Sunday, after he made a last-minute decision to stay home to monitor Hurricane Dorian - and play golf.
Just before flying out on Monday, Pence and Polish Prime Minister Mateusz Morawiecki signed a joint declaration to cooperate on 5G technology, as the US ramps up efforts to combat the influence of Huawei, the Chinese telecoms giant.