Berlin - Chancellor Olaf Scholz reiterated Sunday that Germany will not send fighter jets to Ukraine, as Kyiv steps up calls for more advanced weapons from the West to help repel Russia's invasion.

Scholz only just agreed on Wednesday to send 14 Leopard 2 tanks to Ukraine and to allow other European countries to send theirs, after weeks of intense debate and mounting pressure from allies.

'I can only advise against entering into a constant bidding war when it comes to weapons systems,' Scholz said in an interview with the Tagesspiegel newspaper.

'If, as soon as a decision (on tanks) has been made, the next debate starts in Germany, that doesn't come across as serious and undermines citizens' confidence in government decisions.'

Scholz's decision to green-light the tanks was accompanied by a U.S. announcement that it would send 31 of its Abrams tanks.

Ukrainian President Volodymyr Zelenskyy thanked Berlin and Washington for the move, seen as a breakthrough in efforts to support the war-torn country.

But Zelenskyy immediately stressed that Ukraine needed more heavy weapons from NATO allies to fend off Russian troops, including fighter jets and long-range missiles.

Scholz in the interview warned against raising 'the risk of escalation,' with Moscow already sharply condemning the tank pledges.

'There is no war between NATO and Russia. We will not allow such an escalation,' he said.

The chancellor added that it was 'necessary' to continue speaking with Russian President Vladimir Putin. The last phone call between the leaders was in early December.

'I will talk to Putin by phone again,' Scholz said. 'But, of course, it's also clear that as long as Russia continues to wage war with unabated aggression, the current situation will not change.'