Jens Stoltenberg (Photo: ERA/RONALD WITTEK)

Ukraine's trust in its Western allies, NATO members, has been shaken by delays in arms deliveries and unfulfilled promises, NATO Secretary General Jens Stoltenberg said in an interview with Reuters.

He said that NATO has suffered several setbacks in the issue of supporting Ukraine and needs to review the mechanisms for providing this assistance.

"We need a more robust, institutionalised framework for our support to ensure predictability, to ensure more accountability and to ensure burden-sharing," he said.

As an example of such a "failure," Stoltenberg cited the delay in approving aid to Ukraine in the US Congress. European allies, in turn, provided the Ukrainian army with fewer artillery shells than needed, the NATO Secretary General added.

"Of course, the fact that we have not delivered what we promised has put a dent ... into the trust," he said.

In this regard, Stoltenberg recalled his initiative to create a multi-year plan in which the contribution of each member of the Alliance in support of Ukraine will be clearly defined.

He said the money for Ukraine will be "tiny bits or fractions" of what the United States and its allies have spent in Iraq and Afghanistan.

"There we speak about trillions and ... in Ukraine, we are speaking about billions. But we are actually addressing a real challenge for our security – a more aggressive Russia," the NATO Secretary General explained.

Read also: Ukraine already receiving weapons from new US aid package, White House says