The Biden administration announced a new $400 million military aid package for Ukraine on Friday that includes four more High Mobility Artillery Rocket Systems, or HIMARS.

Ukraine will now have a total of 12 of these precision rocket launcher systems, which have been "especially important and effective in assisting Ukraine in coping with the Russian artillery battle in the Donbas," a senior defense official told reporters Friday.

The rockets have a range of 43 miles. The official said that Ukraine has been striking at Russian targets deep behind enemy lines but has not used them to strike inside Russia.

The new aid package also includes 1,000 new "greater precision" artillery. The name of the system was not shared for security purposes, the official said.

The new aid package is the 15th use of the presidential drawdown authority to give existing U.S. military stocks to Ukraine.

-ABC News' Luis Martinez

Russia considers nuclear weapons only as a deterrent, according to Valentina Matviyenko, Chairman of the Russian Federation Council.

"Russia views nuclear weapons only as a deterrent," Matviyenko said Thursday at a press conference.

The official noted that Russia has “clearly and strictly prescribed those exceptional cases when [nuclear weapons] can only be used in response to -- God forbid that this never happens -- a nuclear attack."

“We behave like a civilized country, and we do it openly,” Matviyenko added.

-ABC News' Edward Szekeres, Yulia Drozd, Max Uzol, and Fidel Pavlenko

Russia claimed no territorial gains in Ukraine on Wednesday for the first time since the beginning of its invasion in late February, the Institute for the Study of War (ISW) said in its latest report.

The Russian Defense Ministry claimed territorial gains every day from the start of the war but has not done so since completing the encirclement of the eastern town Lysychansk on July 3, the ISW said.

The Washington-based think tank said the lull in Russian ground force movements supports its assessment that Russian forces “have largely initiated an operational pause.”

The break in operations is not equal to a complete ceasefire, however, as Russian troops still conducted a number of unsuccessful attacks on all frontlines, the experts added.

Russian troops are instead trying to set up conditions for a bigger offensive as they rebuild their combat power, the ISW report said.

Russia has already increased its fleet in the Black Sea on the shores of Ukraine, local media reported on Wednesday. The Russian naval presence grew by several missile carriers, as well as submarines and an amphibious assault ship.

Ukrainian officials refuted Russian claims on Wednesday according to which Russian troops destroyed two HIMARS multiple launch rocket systems supplied by the United States.

Ukrainian President Volodymyr Zelenskyy added that the Western supplied artillery “started working very powerfully” and at full capacity.

"Finally, it is felt that the Western artillery, the weapons we received from our partners, started working very powerfully," Zelenskyy said in his Wednesday evening address. "Its accuracy is exactly as needed," the president added.

Zelenskyy said the Western weapons have carried out strikes on depots and areas of logistical importance to Russian troops. "And this significantly reduces the offensive potential of the Russian army,” Zelenskyy noted, adding that Russian losses “will only increase every week, as will the difficulty of supplying [Russian troops]."

Ukrainian forces celebrated another symbolic victory on Thursday when they raised their national flag on Snake Island, a recaptured Black Sea isle located 90 miles south of the Ukrainian port of Odesa that became a symbol of defiance against Moscow, according to local reports.

Images released by Ukraine's interior ministry on Thursday showed three Ukrainian soldiers raising the blue and yellow national flag on a patch of ground on Snake Island next to the remains of a flattened building.

But Russia responded to the flag-raising ceremony fast. It said one of its warplanes had struck Snake Island shortly afterwards and destroyed part of the Ukrainian detachment there.

Russia abandoned Snake Island at the end of June in what it said was a gesture of goodwill, raising Ukrainian hopes of unblocking local ports shut off by Russia.

-ABC News' Edward Szekeres, Yulia Drozd, Max Uzol, and Fidel Pavlenko

U.S. Secretary of State Antony Blinken is set to appeal to G20 countries to put pressure on Russia to make it support the U.N. initiative on unblocking the sea lanes for Ukraine and allow grain exports, according to local media reports.

"G20 countries should hold Russia accountable and insist that it supports ongoing U.N. efforts to reopen the sea lanes for grain delivery," said Ramin Toloui, assistant secretary of state for economic and business affairs.

Toloui referred to a U.N. campaign aiming to expedite Ukrainian and Russian exports of harvest and fertilizer to global markets.

Around 22 million tons of grain remain blocked in Ukrainian ports due to the threat of Russian attacks, Ukrainian President Volodymyr Zelenskyy said on Monday.

Ukraine is in active negotiations with Turkey and the U.N. to solve the grain export stalemate, Zelenskyy added.

Blinken is also expected to once again warn China against backing Russia's military campaign in Ukraine.

"[The upcoming G20 summit] will be another opportunity ... to convey our expectations about what we would expect China to do and not to do in the context of Ukraine," the top U.S. diplomat for East Asia, Daniel Kritenbrink, said.

-ABC News' Edward Szekeres, Yuriy Zaliznyak, Max Uzol and Nataliia Kushnir

Ukrainian President Volodymyr Zelenskyy said the former head of the Security Service of Ukraine, or SBU, in Crimea, who was dismissed in the beginning of the Russian invasion, has been notified he is being charged with treason.

"Everyone who together with him was part of a criminal group that worked in the interests of the Russian Federation will also be held accountable," Zelenskyy said during his evening address Sunday. "It is about the transfer of secret information to the enemy and other facts of cooperation with the Russian special services."

A number of Ukrainian public officials have been notified they will be charged for treason and for collaborating with Russia.

-ABC News' Christine Theodorou