LONDON, May 15 - The U.S. and European Union will move to impose heavier economic sanctions on Russia if Moscow or its proxies disrupt Ukrainian presidential election May 25, Secretary of State John Kerry said Thursday.

"I'm not going to get into announcing today what the sanctions are," Kerry said following a meeting in London with his counterparts in Britain, France, Germany and Italy, according to The Associated Press. "We have completed our work. We know what they are. If they have to go into effect, they will have an impact."

A senior State Department official told The Associated Press that the U.S. shared its strategy to use a "scalpel rather than a hammer" to target vulnerabilities in Russia's business, banking, mining, energy, defense or other sectors. The official, who was not authorized to speak by name about the discussions in London, briefed reporters on condition of anonymity.

"Let me emphasize, our hope is not to do this," Kerry said "Our hope is not that we have to go to the next stage. I say to the Russians and everybody, our hope is to de-escalate."

But he added: "If Russia or its proxies disrupt the elections, stand in the way of the Ukrainian people being able to exercise their vote, that is when and if there would be additional sanctions."

Kerry hailed European-backed peace talks on ending Ukraine's crisis. But they began with little promise Wednesday when pro-Russian insurgents - who weren't even invited to the session - demanded that the Kiev government recognize their sovereignty.

The "road map" put forth by the Organization for Security and Cooperation in Europe calls for national dialogue as a first step toward resolving the escalating tensions, in which the insurgents have seized government buildings in eastern Ukraine and declared independence, while government forces have mounted limited offensives to retake control of the region.

Instead of a dialogue, the day was more a case of competing monologues, with the two sides as far apart as ever. Still, Kerry attempted to portray it as a positive step.

"We welcome the successful national dialogue round table in Kiev that took place yesterday and the very good conversation there on decentralization, constitutional reform and the protection of minority rights," Kerry said.

"And we hope that the separatists, we hope the Russians, we hope that others who are disgruntled by what is taking place will take note of a legitimate effort to try to reach out, bring people to the table and find political compromise." (ap/ez)