Pistorius made the statement after taking office on Thursday, the Reuters news agency reported.
He was speaking ahead of a meeting with his US counterpart Lloyd Austin later in the day.
On Friday, defence leaders from about 50 countries and NATO will gather at Germany's Ramstein Air Base to discuss how to provide more weaponry to Ukraine, according to news outlets.
'Our task is to make Bundeswehr strong and support Ukraine'
Speaking after a ceremony with military honours at the German defence ministry, Pistorius said: "These are not normal times, we have a war raging in Europe. Russia is waging a brutal war of annihilation on a sovereign country, on Ukraine."
He added, as quoted by Reuters: "Our task is to make the Bundeswehr [armed forces] strong now, it is about deterrence, effectiveness and readiness. And it is about continuing to support Ukraine, also with materiel of the Bundeswehr."
Pistorius was appointed at a time when Germany is facing pressure from Western allies to permit German-made Leopard 2 battle tanks to be delivered to Ukraine to strengthen Kyiv's defences against the Russian invasion, news outlets reported.
Earlier on Thursday, German President Frank-Walter Steinmeier promised further military assistance to Ukraine and said that Germany’s army must once again become capable of protecting the country, Britain’s The Guardian newspaper reported.
Steinmeier said: “Germany is not at war, but the years of the peace dividend from which we Germans have benefited so long and abundantly are over.”
He cautioned: “We have to respond to threats that also target us.”
Pistorius replaces Christine Lambrecht, who announced her resignation on Monday, after a series of blunders, Reuters reported.
US preparing new USD 2.5bn tranche of security assistance for Ukraine
Meanwhile, the United States is set to finalise a massive military aid package for Ukraine, worth around USD 2.5 billion, broadcaster CNN reported.
The announcement is expected to include, for the first time, Stryker combat vehicles, but not tanks or the long-range missiles that have been sought by Ukraine, according to CNN.
The major new weapons package for Ukraine is set to be unveiled on Friday as defence leaders from around the world gather in Germany to discuss how to help Ukraine in its fight against Russia, the Politico news service reported.
This next tranche will comprise additional artillery, ammunition and armour — likely Stryker armoured combat vehicles — but not the American M1 Abrams tanks, according to Politico.
Ukraine calls on West to supply Leopard tanks
Ukraine’s foreign and defence ministers on Thursday called on Western nations to send German-made Leopard 2 main battle tanks to help their country repel the Russian invasion, the Interfax-Ukraine news agency reported.
Foreign Minister Dmytro Kuleba and Defence Minister Oleksii Reznikov said in a joint statement: "We welcome the bold and very timely decision of the United Kingdom to transfer the first squadron of Challenger 2 tanks to Ukraine. However, it is not sufficient to achieve operational goals.”
The ministers added: “Therefore, we are addressing our appeal to the states that have Leopard 2 tanks in service, including Canada, Denmark, Finland, Germany, Greece, the Netherlands, Norway, Poland, Portugal, Spain, Sweden, and Turkey. We guarantee that we will use these weapons responsibly and exclusively for the purposes of protecting the territorial integrity of Ukraine within internationally recognized borders."
Kuleba and Reznikov also appealed to all states that have the appropriate capabilities to join the initiative to create an international tank coalition in support of Ukraine and make their practical contributions to this initiative, according to Interfax-Ukraine.
European Council head visits Kyiv to discuss EU-Ukraine cooperation
Meanwhile, Charles Michel, the European Council president, travelled to Kyiv on Thursday to discuss the European bloc’s cooperation with Ukraine.
After arriving in the Ukrainian capital, Michel tweeted: “Back in Kyiv to discuss all strands of cooperation. May 2023 be the year of victory and peace.”
Sweden pledges Archer artillery system for Ukraine
Sweden on Thursday announced it would be sending the Archer artillery system for use by Ukraine, a vehicle-mounted self-propelled gun howitzer made by Bofors BAE, The Guardian reported.
At a press conference in Stockholm on Thursday morning, the Swedish government also committed to sending 50 infantry fighting vehicles and 57 NLAW anti-tank robots to Ukraine, according to The Guardian.
Thursday is day 330 of Russia’s war against Ukraine.
Source: Reuters, The Guardian, politico.eu, CNN, politico.com, Interfax-Ukraine