British Foreign Secretary William Hague called this week’s national-dialogue meeting in Kiev “clearly successful” but said the United States and Europe are continuing preparations for “wider economic and trade sanctions” against Russia if it interferes in Ukraine’s May 25 nationwide elections.

Hague, who hosted a meeting here on Ukraine with his counterparts from the United States, Germany, France and Italy, spoke as a shaky quiet fell over eastern Ukraine after the ad hoc talks in Kiev. Pro-Russian militants, who have occupied buildings and skirmished with government forces in eastern Ukraine, did not join the discussions.

The talks marked the tenuous start of a negotiating process being conducted under the auspices of the Organization for Security and Cooperation in Europe. Ukraine’s interim government said it hoped to hold a second such meeting in the coming days in Donetsk, the capital of a region that separatists have declared a sovereign republic. On Thursday, its self-proclaimed “people’s governor,” Pavel Gubarev, promised “total annihilation” of Ukrainian armed forces if they did not abandon checkpoints and pull their troops out within one hour after he spoke.

Steelworkers employed by Ukraine’s biggest tycoon have joined police on patrol in the eastern Ukrainian cities of Mariupol and Makeevka, and the company said its officials had struck a deal with police and pro-Russian separatists in Mariupol for the insurgents to leave occupied government buildings, the Associated Press reported.

The steelworkers are from plants belonging to Metinvest, part of the business empire of Rinat Akhmetov, believed to be Ukraine’s richest man. On Wednesday, Akhmetov issued a statement calling on Donetsk to remain part of Ukraine.

As the Kiev talks were underway, officials in Moscow appeared to soften their stance, at least publicly. In an interview with Bloomberg Television, Russian Foreign Minister Sergei Lavrov said Russia has “no intention” of sending troops into eastern Ukraine, despite Western fears that it will invade after the presidential and mayoral elections set for this month.

Although Western nations have threatened additional sanctions against Russia, Hague said they were not willing to give an “exact definition” of what would provoke them or what form the measures would take.

“If we set a red line, Russia knows that it can go up to that red line,” he said at a news conference. “Efforts to disrupt the election may take many different forms. That’s not something we can define in advance,” but it will be “what determines the attitude of the whole Western world” toward Russia.

In separate comments, Secretary of State John F. Kerry said, “If Russia or its proxies disrupt the election, the United States and those countries represented here today in the European Union will impose sectoral economic sanctions as a result.”

Asked whether the West would be watching for direct Russian interference or hold Moscow accountable for the actions of the pro-Russian separatists, Kerry said a judgment would be made based on “attitude and behavior.”

“I’m not going to start laying out the whole series of definitions except to say to you that it is clear what proxies mean,” he said.

A senior State Department official said earlier that “we have been pretty clear in being able to pinpoint and expose . . . when Moscow’s hand has been behind past disruptions.” The official added, “We’ve seen it in the past — we’ve seen personnel, we’ve seen money, we’ve seen weapons, we’ve seen coordination, we’ve seen actual actors. So all of those things are possible again in this context.”

The official also made clear that threatened sanctions on what President Obama has said would be “sectors” of the Russian economy — including mining, defense, energy and banking — are not likely to be imposed across the board, as in Iran. Instead, the official said, they would “use a scalpel rather than a hammer,” focusing on “new investment” in sanctioned sectors.

The European Union, whose members have far more substantial stakes in the Russian economy than does the United States, has balked at sectoral sanctions and complained that they would unfairly target Europe.

France has indicated that it is likely to go ahead with a $1.6 billion contract, signed in 2009 for delivery this year and next, to supply Russia with two Mistral-class amphibious assault ships, despite U.S. disapproval. Other European countries are concerned about existing contracts for the supply of Russian natural gas.

The official declined to specify whether existing contracts would be exempted from new sanctions.

But the official, speaking on the condition of anonymity to provide background information to reporters, described a far more limited approach than Obama did in his March 20 announcement that he had signed an executive order authorizing sectoral sanctions. Kerry, too, was far more expansive in testimony before the Senate Foreign Relations Committee last month, saying that “the United States and our closest partners are united in this effort despite the costs and willing to put in effect tough new sanctions . . . on key sectors of the Russian economy.”

“In energy, banking, mining — they’re all on the table . . . if Russia does not end its pressure and aggression on Ukraine.”

On Thursday, Kerry would not announce “what the precise sanctions are” but said the administration has decided on them, and that U.S. officials have continued working with the Europeans to ensure they are on board.

“I’m not going to get into characterizations of scalpel or a sledgehammer or whatever, except to say to you that they’re effective, and if they have to go into effect, they will have an impact,” Kerry said.

Anthony Faiola in Kiev, Fredrick Kunkle in Donetsk and Abigail Hauslohner in Moscow contributed to this report.