White House press secretary Karine Jean-Pierre has said that US President Joe Biden and his national security adviser, Jake Sullivan, will meet with NATO Secretary-General Jens Stoltenberg at the White House on Thursday.

Speaking to reporters, Stoltenberg said that he would convene a meeting in Brussels in the coming days with senior officials from Sweden, Finland and Turkey to discuss Turkey’s opposition to Sweden and Finland joining the defence alliance.

On Wednesday, the US unveiled a new $700 million package of sophisticated weapons for Ukraine in an urgent effort to prevent Russia from seizing the final swaths of land in the Donbas region. But the most advanced rocket systems will take at least three weeks to reach the battlefront, raising questions of whether they will arrive in time to stop Russia’s slow but steady gains.

The Biden administration’s decision to send four medium-range rocket systems came after weeks of debate over whether the precision-guided weapons would provoke a strong military reaction from Russian President Vladimir Putin.

“We don’t have an interest in the conflict in Ukraine widening to a broader conflict or evolving into World War Three. So we’ve been mindful of that,” said Colin Kahl, the defence undersecretary for policy. “But at the same time, Russia doesn’t get a veto over what we send to the Ukrainians.”

Still, Kahl and other US officials said that Ukrainian leaders have promised they will use the rockets only to defend their nation.

“The Ukrainians have given us assurances that they will not use these systems against targets on Russian territory,” Secretary of State Antony Blinken said Wednesday. 

However, Kremlin spokesman Dmitry Peskov told reporters Wednesday the US is “deliberately and diligently pouring fuel on the fire.” He added that Russia doesn’t trust Kyiv’s assurances that the multiple rocket launch systems supplied by the US will not be used to attack.

“In order to trust (someone), you need to have experience with situations when such promises were kept. Regretfully, there is no such experience whatsoever,” Peskov said.

The need to train Ukrainian troops on the HIMARS system for about three weeks before they can go to battle raises concerns that Russia will have a window of time to capture key terrain in the east.

“It is a grinding fight,” said Kahl. “We believe that these additional capabilities will arrive in a timeframe that’s relevant and allow the Ukrainians to very precisely target the types of things they need for the current fight.”

The Pentagon would not say how many rockets it will provide to Ukraine, only that it is sending four of the truck-mounted HIMARS systems. The trucks each carry a container with six precision-guided rockets, which can travel about 45 miles (70 kilometres).