LIVERPOOL, England — The top diplomats for the world’s wealthiest large democracies warned Russia on Sunday of “massive consequences” and “severe costs” should it invade Ukraine or continue military aggressions near its border.

The foreign ministers for the Group of 7 urged Russia to pull back from the tense border standoff and made clear that any effort to negotiate or otherwise avoid confrontation would be welcome.

“Any use of force to change borders is strictly prohibited under international law,” they said in a statement. “Russia should be in no doubt that further military aggression against Ukraine would have massive consequences and severe cost in response.”

Their statement largely echoed earlier admonishments by Western officials over the past week after Russia massed as many as 100,000 troops on Ukraine’s eastern, northern and southern borders. On Tuesday, in a two-hour video call, President Biden himself warned President Vladimir V. Putin of unprecedented and painful economic and other sanctions should Russia move in force into Ukraine and called for de-escalation and diplomacy.

But he has promised Mr. Putin some sort of diplomatic discussion of European security, which has already disturbed some American allies.

Mr. Putin has laid out a set of Russian goals that seem impossible to meet, including a written NATO guarantee withdrawing a 2008 NATO pledge to take Ukraine and Georgia into the alliance at some point in the future (a demand already rejected by Washington), and a promise not to deploy weaponry to countries bordering Russia or hold military drills within a certain distance from Russia.

Sunday’s warning also included Japan among the countries now condemning Russia’s military buildup, and it was issued separate from the ministers’ summary of a host of issues discussed — including complicated relations with China and Iran and the ramping up of distribution of the coronavirus vaccine — after two days of meetings in Liverpool, in northern England.

“What we have shown this weekend is that the world’s largest economies are united,” the British foreign secretary, Liz Truss, told reporters in Liverpool. “We have sent a powerful signal to our adversaries and our allies. We have been clear that any incursion by Russia into Ukraine would have massive consequences for which there would be a severe cost.”

The Group of 7 — Britain, Canada, France, Germany, Italy, Japan and the United States — account for about half of the global economy. Diplomats representing the European Union also attended the talks.

Officials have said that Russia’s military could be prepared to invade Ukraine as soon as January or February, although there is no indication that Mr. Putin has made up his mind whether to do so.

Intelligence disclosed by the United States indicated that Russia’s military had developed a war plan that envisioned as many as 175,000 troops pouring across Ukraine’s border — a force that Ukraine’s military, despite U.S.-provided equipment and training, would have little ability to stop.

Mr. Putin has dismissed concerns about the troop buildup on Ukraine’s border, and instead has said the United States and the North Atlantic Treaty Organization are threatening Russia’s security by supporting Ukraine’s military with arms and training.

On Sunday, Mr. Putin’s spokesman, Dmitri S. Peskov, said the Kremlin was prepared to continue what he described as an already substantive conversation about “the confrontational situation that has now emerged in Europe around Ukraine,” according to the Russian news agency Interfax.

Mr. Peskov also said reports about Russian troops on Ukraine’s border were “whipping up information tension.”

“This is precisely done with the aim of further demonizing Russia,” he said in an interview on Sunday, according to the state news agency Tass.

The statement issued by the Group of 7 ministers did not specify what penalties Russia would face should it invade. The White House has warned that it is prepared to take steps against Russia, also unspecified, that the United States resisted in 2014, after Mr. Putin’s government annexed the Crimean Peninsula in Ukraine. It could also lead NATO to reposition its troops in Europe.

A senior State Department official who attended the talks in Liverpool said the joint statement showed that the Group of 7 and the European Union were “absolutely united” in imposing tough penalties against Russia if necessary. It was a noteworthy description, given debate over cutting off Russia from the global financial settlement system, known as SWIFT, that some European officials have feared might provoke too harsh a response.

“We reaffirm our unwavering commitment to Ukraine’s sovereignty and territorial integrity,” the statement said, adding that the signatories would “intensify our cooperation on our common and comprehensive response.”

The senior State Department official described the summit as “a very intense round of meetings” that also highlighted concerns about commandos working for the Wagner Group, a Kremlin-linked private mercenary force, in Libya and elsewhere in Africa. The official accused the private force — which has also deployed to conflict zones in Belarus and across the Middle East to further Russia’s interests — of “causing extreme problems” in the Sahel, but did not elaborate.

The official briefed reporters traveling with Secretary of State Antony J. Blinken on the condition anonymity to more openly discuss the diplomatic talks in Liverpool.

The State Department is dispatching a senior official this week to Kyiv, the Ukrainian capital, and Moscow for talks to try to ease tensions. But the trip, by Karen Donfried, the assistant secretary of state who oversees American policy in Europe, will also “reinforce the United States’ commitment to Ukraine’s sovereignty, independence and territorial integrity,” the department said in a statement.

Diplomats in Liverpool also discussed ways to counter what was described as China’s human rights abuses and predatory economic partnerships with developing countries, as well as how to speed humanitarian aid to Afghanistan, which is facing vast food shortages, while holding the Taliban to account.

Additionally, Ms. Truss, the British foreign secretary, repeated her warning that the latest rounds of nuclear talks between world powers and Iran represented Tehran’s “last chance to come to the negotiating table with a serious resolution.” Diplomats are trying to revive the 2015 accord — from which the Trump administration withdrew the United States in 2018 — that limited Iran’s nuclear program in exchange for easing American financial sanctions.

But eight months of negotiations after Mr. Biden took office, and signaled his intent to rejoin the deal, were dealt a severe, and perhaps fatal, setback by new leaders in Iran who are demanding that the sanctions be lifted before agreeing to other conditions.

The talks, in their seventh round, continued on Sunday in Vienna. They recently resumed after a break of more than five months as Iran elected a new harder-line government.

Germany’s new foreign minister, Annalena Baerbock, said in Liverpool that “time is running out” for a deal. Iran has moved to reject compromises reached in earlier rounds, she said. The latest round, she told reporters, “has shown in the last days that we do not have any progress.”

China and Russia have indicated more patience with Iran, saying that the talks are proceeding, if slowly.

“There is still time for Iran to come and agree this deal,” Ms. Truss said.

The senior State Department official said the discussions in Liverpool included options for action against Iran should the nuclear talks fall apart.

Steven Erlanger contributed reporting from Brussels, and Mark Landler from London.