KIEV (Reuters) - Ukraine has secured U.S. assurances that President Donald Trump will not betray its interests when he holds his first bilateral summit meeting with Russian leader Vladimir Putin in Helsinki on July 16.

FILE PHOTO: U.S. President Donald Trump shakes hands with Ukraine's President Petro Poroshenko in the Oval Office at the White House in Washington, U.S. June 20, 2017. REUTERS/Jonathan Ernst/File Photo

But Trump is known for his spontaneous and sometimes erratic style of doing diplomacy, and Kiev fears that behind closed doors he may prove susceptible to Putin’s efforts to win U.S. acceptance of Russia’s 2014 annexation of Crimea from Ukraine.

Trump and Putin will discuss a range of issues including arms control, Syria and U.S. economic sanctions against Moscow at their summit, which could potentially prove a game-changer for Ukraine.

“We received clear assurances from the American side that Ukrainian interests will be confirmed and protected (at the summit),” said a Ukrainian diplomat, speaking on condition of anonymity because of the sensitivity of the matter.

“It is important for us that no nasty surprise happens behind our backs, and we received assurances (from the U.S. side) that this will not happen.”

Kiev has counted on U.S. diplomatic and financial support in its standoff with Moscow since the annexation of Crimea and the outbreak of Russian-backed separatist fighting in eastern Ukraine that has killed more than 10,000 people despite a notional ceasefire.

Kiev and Washington accuse Russia of sending troops and arms to Ukraine’s eastern Donbass region, which Moscow denies.

Ukraine hopes Trump will push Putin to scale back Moscow’s support for the separatists in eastern Ukraine and to soften his position regarding the deployment of a peacekeeping mission to that region.

SUPPORT

Some comments Trump made on the presidential election campaign trail in 2016 made Ukrainians nervous about a Trump presidency, but such worries have proved premature.

Kiev has continued to enjoy strong bilateral support from the United States, and sanctions imposed against Russia after the Crimea annexation have been strengthened, not, as some feared, lifted.

In Kurt Volker, Washington appointed a hawkish special envoy to the Ukraine conflict after Trump’s election victory, and went as far as providing military aid to Ukraine, a step Trump’s predecessor Barack Obama had shied away from taking.

Also, any concession Trump might want to make to Putin would likely meet resistance in the U.S. Congress.

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But Trump’s unpredictability and capacity to cause ructions among Washington’s allies will give Ukraine pause for thought.

Asked in June if the United States would recognize Crimea as part of Russia, Trump said: “We’re going to have to see.” A White House spokesman later stressed Washington would not recognize the Crimea annexation.

Anton Gerashchenko, a prominent Ukrainian lawmaker, said any decision by Trump to support Putin’s interests in Ukraine would “extremely negatively affect all U.S. positions in the world because America was believed only when they defended their allies with their own strength”.

“Ukraine, one way or another, is an ally of the United States,” he told the television channel 112. “President Obama did not protect us, he let Putin freely capture Crimea and did not support us to the proper extent.”

Trump’s meeting with Putin will take place after a potentially fractious NATO summit in Brussels this week, where the president is likely to press Washington’s allies to spend more on defense.

German lawmakers and security experts fret that Trump could take decisions with Putin at their meeting without consulting his NATO allies. Ukraine is not a NATO member.