MUNICH, Germany — Serious Cold War-like tensions consumed a key international security conference Saturday as the United States and its allies traded blame with Russia for the fighting in eastern Ukraine, fueling uncertainty over a new Franco-German diplomatic drive to end the worst bloodshed in five months.

The differences were underlined in terse speeches and a burst of derisively undiplomatic laughter that greeted Russian Foreign Minister Sergei Lavrov’s claim that Russia’s annexation of Crimea last year followed a legitimate vote – held under the guns of thousands of Russian troops and unrecognized internationally – for self-determination.

“Well, you might find it funny. I also find many things you said funny,” responded a steely-eyed Lavrov, who repeated charges that the United States and the European Union bore responsibility for the fighting, the overall downturn in relations and other disputes. He repeated anew Moscow’s denial that Russian forces were in eastern Ukraine.

Vice President Joe Biden, the most senior U.S. official at the yearly international confab, warned that “the United States and, God willing, all of Europe and the international community will continue to impose costs” on Russia until it stops providing troops and arms to separatists who’ve rolled up new territory in an offensive launched late last year.

“Too many times, President (Vladimir) Putin has promised peace and delivered tanks or troops and weapons,” said Biden.

The depth of the East-West tensions over Ukraine was underscored by the relative lack of attention at this year’s Munich Security Conference to other international crises, including the threat posed by the Islamic State, the war in Syria, the Iran nuclear dispute and the Ebola outbreak in West Africa.

It remained uncertain if the Obama administration would grant Ukrainian President Petro Poroshenko’s request for defensive equipment to blunt the superior armor, artillery and troops that the NATO allies charge Moscow is providing the separatists.

The U.S. decision appeared to hinge on the outcome of the new peace initiative that German Chancellor Angela Merkel and French President Francois Hollande took Friday to Putin in Moscow. The three were to consult on the plan in a conference call Sunday with Poroshenko. Merkel then is to travel to Washington for talks with President Barack Obama on Monday.

The initiative aims to implement a much-breached ceasefire accord reached in September in Minsk, Belarus.

Merkel and other European leaders oppose providing lethal weapons to Ukraine. But Poroshenko appeared to offer an out, telling the conference that he just wanted radios that Russia couldn’t monitor or jam and radar that would allow his forces to determine the positions of enemy artillery and fire back.

“We will not use the defensive equipment to the attack,” he said. “The stronger our defense, the more convincing is our diplomatic voice.”

Biden, who held talks with Secretary of State John Kerry and Poroshenko on the sidelines of the conference, appeared deliberately vague on the issue.

“We will continue to provide Ukraine with security assistance, not to encourage war, but to allow Ukraine to defend itself,” Biden said, without distinguishing between lethal weapons and the non-lethal supplies, like night vision goggles, that Washington is providing Kiev.

More than 5,300 people have died and tens of thousands displaced since April, according to United Nations data, when fighting erupted as pro-Russia separatists declared independence for the eastern regions of Lugansk and Donetsk following Russia’s seizure of Crimea.

The crisis in the former Soviet republic erupted after former Ukrainian President Viktor Yanukovych reneged under Russian pressure on a pledge to sign an accord opening the door to Ukraine’s admission to the EU. He fled the country when months of peaceful protests turned violent after police attacked demonstrators.

Lavrov repeated Russia’s claims that Yanukovych was ousted by a U.S.-backed coup and replaced by an ultra-nationalist regime that threatens Russian-speakers and other minorities.

Poroshenko said that the initiative called for establishing a ceasefire along the current battle lines, and that the sides would gradually pull back to the positions they held when a truce accord was reached in Minsk.

The vacated territory would apparently become a demilitarized zone of up to 44-miles wide to which Hollande referred in an interview with France 2 TV. Hollande said the Franco-German plan would provide greater autonomy for Donetsk and Lugansk.

The Minsk accord also called for Ukraine to resume control of the border with Russia under monitoring by international observers.

Addressing the conference after returning from Moscow, Merkel said the new initiative’s success was “uncertain.”

She reaffirmed her opposition to arming the Ukrainian military with anti-tank weapons and other lethal arms, an idea that is being considered by Obama and is being pushed by many lawmakers from both parties, some U.S. diplomats and some senior U.S. military officials.

Asked by Senate Foreign Relations Committee Chairman Bob Corker, R-Tenn., about the issue, Merkel replied: “I’m fairly concerned that this conflict cannot be solved by military means.”

“I believe that more weapons will not lead to the progress Ukraine needs,” she said to applause that illustrated European opposition to the idea.

Merkel was pressed by former British Foreign Secretary Malcomb Rifkind on how Putin could be compelled to uphold a peace deal if the Ukrainian military, equipped with obsolete weapons, was unable to defend itself against superior Russian arms.

“I can’t envision any situation in which a better-equipped Ukraine military would convince President Putin that he could lose militarily,” she said.

Many European officials and U.S. officials agree. They fear that supplying Ukraine with arms would give Putin an excuse to openly intervene in Ukraine and clamp down harder at home as Russia’s economy is battered by collapsing oil prices and U.S. and European sanctions aimed at reversing his annexation of Crimea and curtailing support for the separatists.

Lavrov appeared to play on those fears, saying that giving weapons to Kiev “will only exacerbate the tragedy of Ukraine.”

At another point, he said Ukrainian leaders shouldn’t let U.S. and EU support “go to their heads the way it went to Saakashvili’s head in 2008 and we know how that ended.” He was referring to the Russian invasion that defeated a bid by then Georgia President Mikheil Saakashvili to secure the breakaway South Ossetia region.

At the same time, Lavrov held out hope for the new peace initiative.

“These talks will continue as you know; we believe there is every possibility that we will reach a result and agree [on] the recommendations that will allow the sides to really untie this knot of a conflict,” he said.

Supporters insist that providing the Ukrainian military with weapons would raise the costs to Russia and its proxies high enough to compel Putin to adhere to a settlement.

Sen. Lindsey Graham, R-N.C., took Merkel to task for trusting Putin, adding his voice to those who hold Russia primarily responsible for the failure of the Minsk accord.

“At the end of the day, to our European friends, this is not working. You can go to Moscow until you turn blue in the face. Stand up to what is clearly a lie and a danger,” Graham told the conference.

Biden took a hardline in a speech reminiscent of the Cold War, including charges that Putin has resorted to the Soviet era tactic of stifling dissent by confining critics in psychiatric hospitals.

“America and Europe are being tested,” said Biden. “President Putin has to understand that as he has changed so has our focus. We have moved from resetting this important relationship to reasserting the fundamental bedrock principles on which European freedom and stability rest.”