KYIV, Jan 3 - Ukrainians on the frontlines anticipate that the forthcoming battles against Russia will require advanced weapons — tools Kyiv continues to ask the U.S. and Western allies to ship so it can press forward in the country’s east.

Michael Carpenter, U.S. ambassador to the Organization for Security Cooperation in Europe, said the Biden administration is looking to provide “sustainable” assistance to Ukraine, even if sometimes it’s not always the amount Kyiv hopes for, POLITICO reported.

“The Pentagon has been advising the Ukrainians on what they think is the most sustainable type of support that we can provide. And it has to do with the numbers of the equipment and artillery, munitions that we have available and the pace at which we can continue to expand those sorts of munitions and hope for replacements,” Carpenter said. “You have to factor in costs. The enemy certainly factors in costs.”

To date, the U.S. and Europe have balked at sending long-range missiles to Ukraine. Biden administration officials, in particular, are fearful of provoking Russian President Vladimir Putin further. And some European countries are increasingly concerned about the economic costs of sending more high-value weapons to Ukraine as well as increasing commitments to fleeing Ukrainians.

Carpenter repeated President Joe Biden’s refrain that the U.S. will back Ukraine “for as long as it takes” alongside its European partners — despite some of the hardships.

“We understand that for some countries, this means that heating costs are going to be higher this winter. But Ukrainian men, women and children are being tortured and being killed,” Carpenter said. “The sacrifices that they're making are orders of magnitude larger than the ones that we are making in our countries. We are trying to share the burden amongst ourselves so that it's equally distributed.”

Despite the winter weather conditions in Ukraine, the country’s armed forces are still engaged in intense battles with Russia, particularly in the city of Bakhmut. The fighting is likely to drag on through the winter.

Carpenter said the U.S. is working with the Ukrainians, the U.N., the Europeans and human rights organizations to investigate Russian war crimes. However, the process for prosecuting potential crimes could take years.

“The scale and scope of what we're seeing is just so enormous that it's going to require multiple different mechanisms and jurisdictions to get involved in order to ensure that there is some accountability for these horrific war crimes and what are quite likely crimes against humanity,” Carpenter said. (po/ez)