KIEV (Reuters) - Outgoing U.S. Vice President Joe Biden called on Monday for sanctions on Russia to stay, urging the world to stand up to its “coercion and aggression” after President-elect Donald Trump mooted ending the measures under a possible deal with Moscow.

Speaking on a swan song visit to Kiev, Biden said the G7 nations and European Union should lift the sanctions only after Russia had fully implemented a peace deal on ending a separatist rebellion in eastern Ukraine and returned control of Crimea.

Trump, who will be inaugurated on Friday, raised the prospect that he would propose offering to end the sanctions imposed over Russia’s 2014 annexation of Crimea and its role in the rebellion in return for a nuclear arms reduction deal.

Without mentioning Trump, Biden appeared to take issue with the President-elect’s comments made in an interview published in Monday’s edition of the Times of London.

“The international community must continue to stand as one against Russian coercion and aggression,” he told reporters, standing alongside Ukrainian President Petro Poroshenko.

Biden stressed the 2015 deal on ending the rebellion by pro-Russian insurgents which is still continuing, with Washington accusing Moscow of failing to keep its side of the bargain.

“Together with our EU and G7 partners, we made it clear that sanctions should remain in place until Russia fully, emphasize fully, implements its commitments under the Minsk agreement,” he said, adding that Crimea-related sanctions must also stay “until Russia returns full control to the people of Ukraine”.

U.S. support for Ukraine has contributed to a deterioration in relations with Russia to their worst since the Cold War.

Under President Barack Obama, Washington has invested heavily in helping Kiev make a success of a 2013-2014 uprising which forced a Kremlin-backed leader to flee and installed the pro-Western opposition in power.

Ukrainian President Petro Poroshenko (R) and U.S. Vice President Joe Biden attend a news conference in Kiev, Ukraine, January 16, 2017. REUTERS/Gleb Garanich

Trump’s open admiration of Russian President Vladimir Putin and stated desire to improve bilateral ties have stoked fears in Kiev that U.S. resolve to hold Russia to account could waver.

Biden has mixed support with some tough talking about Ukraine’s patchy efforts in tackling graft, and has previously warned that international help is conditional on Kiev making good on promises to tackle endemic bribe-taking.

“You’re fighting ... the cancer of corruption,” Biden, who leaves office on Jan. 20 along with Obama, said on Monday.

HOPE SPRINGS ETERNAL

Poroshenko said Ukraine believed in good cooperation with the new U.S. administration and urged sanctions to stay, without mentioning Trump’s remarks on a deal with Russia. A Kremlin spokesman said it was too early to comment.

Biden has been the front man for U.S. policy towards Ukraine, visiting Kiev five times since the change in power and maintaining such regular telephone contact with Ukrainian officials that he has joked he talks to them more than his wife.

As Biden left the room, a journalist asked if he thought the Trump administration would give Ukraine the same priority as he had. Biden gave a thumbs up and said: “Hope springs eternal.”

Continued Western support is vital for Ukraine. The economy, which has been badly hit by the war in the east, is slowly emerging from two years of recession but remains dependent on external financial help. The United States has so far provided over $3 billion and said it could offer more, provided reform efforts continue.

Andy Hunder, the head of the American Chamber of Commerce in Ukraine, said Kiev would have to put much time and resources into dealing with the new U.S. administration.

“On Jan. 20 Ukraine will be waking up to a new reality,” he told Reuters. “There is a concern in Kiev about how the new relationship will develop. It will require building new bridges to the influencers, the gatekeepers and decision-makers.”

Kiev has already taken steps to win the good favor of the those calling the shots in the Trump administration. Days after his election in November, Poroshenko’s office started planning an official visit to Washington in early 2017.

The Ukrainian government has hired former Republican National Committee chairman Haley Barbour and his lobbying firm BGR Group to lobby U.S. politicians and arrange meetings between U.S. and Ukrainian officials.

This is not to say that Ukraine lacks senior political advocates in the United States.

A bipartisan group of U.S. senators, including John McCain and Marco Rubio, said last week they wanted to slap a wide range of sanctions on Russia over its cyber activities and actions in Ukraine and Syria.

A sanctions bill with similar provisions is being written in the House of Representatives.

“Our job is to make sure this attention on Ukraine does not wane,” Ukraine’s Ambassador to the United States, Valeriy Chaliy said on Wednesday.