By Tom Balmforth
KYIV (Reuters) -Ukraine will now push for Western fourth generation fighter jets such as the U.S. F-16 after securing supplies of main battle tanks, an adviser to Ukraine's defence minister said.
Ukraine won a huge boost for its troops on Wednesday as Germany and the United States announced plans to provide heavy tanks for Kyiv, ending weeks of diplomatic deadlock on the issue.
"The next big hurdle will now be the fighter jets," Yuriy Sak, who advises Defence Minister Oleksiy Reznikov, told Reuters by phone.
Ukraine's Air Force has a fleet of ageing Soviet-era fighter jets that came off the assembly line before Kyiv even declared independence more than 31 years ago. The warplanes are used for intercept missions and to attack Russian positions.
"If we get them (Western fighter jets), the advantages on the battlefield will be just immense... It's not just F-16s (U.S. multirole fighter jets): fourth generation aircraft, this is what we want."
Western military support has been vital for Kyiv and has rapidly evolved during the war. Before the invasion, even the idea of supplying lethal aid to Ukraine was highly controversial but Western supplies have since shattered taboo after taboo.
"They didn't want to give us heavy artillery, then they did. They didn't want to give us Himars systems, then they did. They didn't want to give us tanks, now they're giving us tanks. Apart from nuclear weapons, there is nothing left that we will not get," Sak said.
Ukraine, which was invaded by Russia last February, has also said it wants to receive long-range missiles from the West.
Moscow reacted furiously on Wednesday after Germany approved the delivery to Ukraine of Leopard 2 tanks, the workhorse of armies across Europe, in a decision that is certain to gird Ukraine's offensive power.
Justin Bronk, a researcher at the RUSI think tank in London, said Ukraine's Air Force would benefit greatly from Western fighters in terms of air-to-air and potentially air-to-ground lethality.
But he said on Twitter they would still be at high risk from Russian surface to air missiles, forcing them to fly very low near the front line, something that "would dramatically reduce effective missile range and limit strike options".
Deputy White House national security adviser Jon Finer told MSNBC on Thursday that the United States would be discussing the idea of supplying fighter jets "very carefully" with Kyiv and its allies.
"We have not ruled in or out any specific systems. We have tried to tailor our assistance to the phase of the fight the Ukrainians are in," Finer said.
Sak said he expected the United States could play a key role in getting a decision to supply fighter jets over the line.
Despite any lack of significant palpable movement on the matter, Ukraine's Air Force has yearned for better aircraft throughout the war.
A Ukrainian pilot codenamed Juice told Reuters last month that many of his peers in the Air Force were taking English lessons in their free time in anticipation that Kyiv would one day receive foreign aircraft such as the F-16 fighter.