The warning came as a result of the Group of Seven's concern that an invasion could have "massive implications" and cause Moscow severe economic hardship.
The United States, Britain, and the rest the G-7 foreign ministers joined together by the European Union's chief of foreign affairs and issued a joint statement condemning Russia's aggression towards Ukraine and urging them to "unify in our condemnation."
The G-7 urged Russia to "de-escalate and pursue diplomatic channels" and to abide by its international obligations on transparency of military activities. They also praised Ukraine for "restraint."
International law prohibits any use of force to alter borders. Russia should know that any further military aggression against Ukraine will have severe consequences and a high cost response," the statement stated.
Russia's movements of weapons and troops towards the border region dominated weekend discussions among foreign ministers of the G-7 rich democracies in Liverpool.
The U.S., along with its allies, are concerned that Russia's buildup could lead to an invasion and have pledged to impose severe sanctions on Russia's economy.
Moscow denies any plans to attack Ukraine, and Kyiv is accused of having its own aggressive designs.
The conference host Liz Truss, British Foreign Secretary, stated that the G-7 was sending "powerful signals to our adversaries as well as our allies".
Although the statement promised a "common, comprehensive response", it did not provide any details. Truss stated that the G-7 was considering all options when it comes to economic sanctions. Antony Blinken, the U.S. Secretary Of State, stated on NBC's Meet the Press that "we are ready to take the types of steps we haven't taken in the past" if Russia doesn't respond.
The U.S. and its allies are avoiding any talk of a military intervention to protect Ukraine. Instead, efforts focus on harsh sanctions that would affect the Russian economy and not just individuals.
On Saturday, U.S. reporters asked President Joe Biden about the possibility that combat troops could be sent to Ukraine. He said that this idea had never been considered. He asked, "Are we ready to send American troops to war and go into Ukraine in order to fight Russians on a battlefield?"
Biden spoke on video to Russian President Vladimir Putin last week and said that he had made it clear that in case of invasion, the economic consequences for Putin's economy would be "devastating." Devastating."
Truss stated that Biden had told Putin that the U.S. position "carries the support from the G-7 countries in general." This should concern Vladimir Putin.
The meeting of top diplomats from the U.K. and other countries was held at the Dockside Museum of Liverpool. They discussed China's aggressive behavior in the Indo-Pacific and the Iran nuclear deal.
It has been difficult to get a united response from the G-7, which is a group of countries that have different interests, to global crises.
Germany intends to get gas from Russia through the controversial Nord Stream 2 pipeline. This pipeline bypasses Ukraine. However, Blinken stated that it was difficult to envision the pipeline being operational "if Russia renews its aggression on Ukraine or if it takes new action."
He said, "So I think that President Putin must also factor this in, as he's considering what he will do next."
Britain, while not dependent on Russian gas for its energy, has also criticized the pipeline. However, there are tricky questions regarding London's financial district, and London's property market, which are both hubs of Russian money.
The U.K. financial and banking authorities have been long criticised for their alleged indifference to ill-gotten profits.
Truss stated that Britain has "very strict anti-corruption, anti-money laundering rules" but also mentioned that Russian money and Russian gaz came at a high cost.
She stated that "we cannot have short-term economic gain at our expense of long-term freedom and democracy."
G-7 countries are increasingly concerned about China’s increasing economic and technological dominance in developing countries. As an alternative to China's money, the G-7 launched the "Build Back Better World" initiative. This will provide funding for large infrastructure projects in developing countries.
Truss also invited Ministers from the Association of Southeast Asian Nations (ASEAN) to Liverpool's meeting. Truss stated that the G-7 was concerned about China's coercive economic policy.
She stated that the positive agenda she has set is to ensure countries have other sources of investment and trade. "And that we are making sure that we abide -- and ensure that others are adhering to -- the rules-based international system" of trade.
However, a united stance toward China remains difficult to achieve, with the U.S., Britain, and other G-7 members being more hawkish than others.