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- Russia is pushing back Ukraine's military on key parts of the front line.
- A US military official told CNN that US aid arrived too late to stop Russia from advancing.
- Some analysts believe that when US aid does arrive in quantity, the situation will stabilize.
The delay by the US Congress in approving a vital aid bill means Ukraine is now struggling to fight back Russian advances, a former US military official said.
In an interview with CNN, retired US Air Force Col. and military analyst Cedric Leighton discussed Ukraine's increasingly desperate attempts to hold back Russian advances near Kharkiv, Ukraine's second biggest city.
He said that the delay in passing the $61 billion US aid bill, which was approved in April after being blocked for months by Republicans, had placed Ukraine at a disadvantage.
"The delay in aid was, frankly an inexcusable pause in the ability of the Ukrainians to fend off Russian advances. And right now what it means is that the Ukrainians are on the backfoot," said Leighton.
Kharkiv, which is situated near the Russian border in northern Ukraine, has been the focus of intensifying Russian attacks in recent days. Its forces are also making gains on other parts of the front line.
Russia is seeking to exploit weaknesses in Ukraine's military, which is running low on crucial air defense and ammunition supplies as a result of the aid block.
US officials told The New York Times that significant amounts of aid might not begin to arrive at the front line until July, but that the situation would likely stabilize in the long term.
Until then, Ukraine faces serious problems. In particular, Leighton singled out air defense as a key issue, with Russia using plane-launched "glide bombs" to devastate Ukrainian positions.
"The Russians have been able to exploit the air defense weaknesses in Ukraine, and because of that, they are able to advance because they have air cover," said Leighton.