US Vice President Joe Biden (L) talks with Ukrainian Prime Minister Arseniy Yatsenyuk on December 7, 2015, during a three-day working visit intended to signal support for Kiev amid its ongoing clash with Moscow
Kiev (AFP) - US Vice President Joe Biden said Monday that Washington remained determined to see Russia adhere to a shaky Ukrainian peace agreement and hand back Crimea to Kiev.
Biden's visit is his fourth to Kiev since Russia annexed Ukraine's Black Sea peninsula in March 2014 and then watched with approval as pro-Kremlin fighters carved out their own region in the eastern industrial heart of the ex-Soviet state.
The war-scarred nation now fears slipping off the global radar due to recent international efforts to enlist Moscow in a joint fight against the Islamic State (IS) group in Syria and Iraq.
But Biden brought a message of reassurance to Kiev.
"The US stands firmly with the people of Ukraine in the face of continued -- I emphasise continued -- aggression from Russia and Russian-backed separatists," he told Ukrainian President Petro Poroshenko.
Washington's EU allies support Ukraine's view of Russia orchestrating and backing 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 remaining Middle East ally by targeting Syria's Western-backed rebels instead of extremist groups.
- 'Hold Russia accountable' -
Yet the Islamic State's claim of downing a Russian airliner carrying 224 people over Egypt on October 31 appears to have prompted Moscow to focus more on bombing IS's oil infrastructure and other jihadist targets.
The November 13 Paris attacks the IS also claimed saw France make a push to enlist Russia in a "grand coalition" against the jihadist group alongside the United States and some European and Arab states.
Biden said the latest developments in the Middle East in no way appeased Washington's anger with Putin or slackened its support for Poroshenko's pro-Western team.
"The invasion by Russia of Crimea will not be accepted by us or by the international community. This attempted annexation is contrary to international law, is wrong, and will not be accepted in any circumstance," he said.
Biden also hinted that Russia may face additional US sanctions if its peace commitments were not met.
Washington was in contact with "our fellow leaders around the world... to make sure the international community stands and holds Russia accountable for the actions against Ukraine," Biden said after meeting with Ukrainian Prime Minister Arseniy Yatsenyuk.
"If they do not meet their obligations, (one must) increase the price Russia has to pay for its illegal actions internationally."
- The 'cancer' of corruption -
Biden also spoke out on the issue of graft in a country where morale is sagging due to Poroshenko's seeming inability to tackle the corruption that has plagued Ukraine for much most of its recent years.
Poroshenko's prosecutor general has been accused of blocking investigations and hiring workers who have since been detained with huge stashes of gold and cash in their flats.
"It's absolutely critical for Ukraine... to root out the cancer of corruption," the US vice president said.
"There's a growing degree of popular frustration about the slow pace of the reforms and the efforts to root out corruption," Biden warned.
Poroshenko said he agreed that the 19-month war in which more than 8,000 have died "cannot be used as an excuse for failing to conduct reforms."