US Vice President Joe Biden meets Ukrainian leaders on Monday to kickstart their drive against corruption and reassure them of Western support in the face of the current focus on Syria.
Biden's visit is his fourth to Kiev since Russia annexed Ukraine's Crimea peninsula in March 2014 and then watched with approval as pro-Kremlin insurgents carved out their own region in the eastern industrial heartland of the ex-Soviet state.
He met Ukrainian President Petro Poroshenko in private early Monday and will speak to Prime Minister Arseniy Yatsenyuk before delivering a highly anticipated address to parliament the following day.
"We do not know if there is any other historical precedent for a foreign official giving a speech like this," said one senior US administration official in a teleconference with reporters.
Washington and Kiev's EU allies support Ukraine's view of Russia being an "aggressor" that orchestrated the separatist revolt in reprisal for the February 2014 ouster of a Moscow-backed president -- an assertion the Kremlin denies.
Both Washington and Brussels have slapped stiff economic sanctions on Russian President Vladimir Putin's inner circle and have helped train and equip Ukraine's underfunded army with defensive equipment such as advanced radar.
But the situation changed when Russia began launching ferocious air strikes against Syrian President Bashar al-Assad's foes on September 30.
Washington accused Putin of trying to prop up his most important Middle East ally by targeting Western-backed Syrian rebels instead of ISIS and other extremists occupying swathes of Syria and Iraq.
Yet ISIS claim of downing a Russian airliner carrying 224 holidaymakers and crew from Egypt on October 31 appears to have prompted Moscow to focus more on bombing the ISIS oil infrastructure and other jihadist targets.
The November 13 Paris attacks further prompted French President Francois Hollande to try and enlist Russia in a "grand coalition" against the IS that included the United States and some European and Arab states.
Hollande's mission has been treated with caution by the White House and overt fright by Ukraine.
The senior US official said Biden would take extra care to stress that the overtures toward Putin in no way affected the West's backing of Kiev.
"I think that is going to be a major theme of the trip -- that nothing that is going on in the Middle East has changed one iota of our commitment to the Ukrainian people and to their security," the US official said.
Yatsenyuk added in a televised address on Sunday that "Russia's plan to erase Ukraine from the global radar (has failed) thanks to latest visits by our European partner and -- most importantly -- US Vice President Joe Biden."
Yet Biden arrives in a 40-million-strong country whose morale is sagging due to Poroshenko's seeming inability to erase corruption that has plagued Ukraine for much of its recent history.
Poroshenko's prosecutor general has particularly fallen prey to accusations of blocking investigations and hiring workers who have since been detained with huge stashes of gold and cash in their flats.
Both this and Kiev's futility in winning back the east after 19 months of bloodshed that has claimed more than 8,000 lives is souring the public's mood toward the government and helping the resurgence of Ukrainian far-right groups.
"Much more needs to be done to reform the prosecutor-general's office so that it actually enables anti-corruption efforts as opposed to standing in (their) way," the US official said.
Some analysts said the problem rested in Kiev's ineffective bid to break the grip a handful of tycoons have enjoyed over the state's politics by indirectly controlling its main firms.
"Ukraine has 1,833 state corporations that are a persistent source of corruption," said Anders Aslund of the US-based Atlantic Council.
"The government has failed to privatise one single enterprise because of deeply ingrained vested interests."
And even some of the president's backers agree.
Western "fatigue with Ukrainian corruption has reached a critical level," pro-Poroshenko lawmaker Sergiy Leschenko wrote on Facebook.