The US think tank made the assessment in its latest report on Wednesday night.
Ukrainian and Russian forces continue to clash in positional engagements along the entire front, the ISW said.
On Wednesday, positional battles took place along the Kupyansk-Svatove-Kreminna line in Ukraine's eastern Luhansk region, but there were no confirmed changes in this area, according to US analysts.
Ukrainian and Russian forces on Wednesday also continued positional engagements near Avdiivka, in the eastern Donetsk province, and in the southeastern Zaporizhzhia region, the ISW added.
There were no confirmed changes to the frontline in these areas, either, the US think tank reported.
Meanwhile, Russia recently made some gains southwest of Bakhmut, and southwest of Donetsk City, in Donetsk province, and in the east (left) bank of the southern Kherson region, near Krynky, according to the ISW.
In all, Ukrainian and Russian forces on Wednesday clashed in 73 combat engagements, the General Staff in Kyiv said.
Thursday is day 687 of Russia’s war on Ukraine.
Russia invaded Ukraine on February 24, 2022, launching the largest military campaign in Europe since World War II.
Source: ISW, The General Staff of the Armed Forces of Ukraine