President Joe Biden had his first official call as the head of the U.S. government with Russian President Vladimir Putin that sources said touched on confrontational topics as well as arms control.

Sources with knowledge in the matter said that Biden discussed topics such as the renewal of a nuclear arms treaty, the 2020 U.S. presidential elections, and the war in Afghanistan.

Biden's priority during the call was reportedly to restart talks over the U.S. and Russia's only remaining nuclear arms treaty. Sources said that Biden intends to bring back Russia to the negotiating table and rebuild diplomacy.

The New Strategic Arms Reduction Treaty or START nearly crumbled after former President Donald Trump expressed his intention of abandoning the agreement, which is set to expire next month. Trump initially said that the U.S. would not renew the treaty unless China joined.

White House officials said Wednesday that Russia had agreed to cooperate and "work urgently" to extend the treaty. Officials said in a statement that Russia and the U.S. have agreed "to explore strategic stability discussions on a range of arms control and emerging security issues."

Apart from the nuclear deal, Biden also addressed some very sensitive topics during his call with Putin. This included the recent SolarWinds hack, believed to have been perpetrated by Russian government operatives. He also discussed with Putin reported bounties placed by Russia on several U.S. soldiers in Afghanistan.

"President Biden made clear that the United States will act firmly in defense of its national interests in response to actions by Russia that harm us or our allies," the White House said.

During his campaign, Biden had often criticized Trump for his weak stance on Russia. Biden had called Trump "Putin's puppy" during the first presidential debate.

Biden has expressed his condemnation of some of Russia's recent actions, including the poisoning of Russian opposition leader Aleksei Navalny. Biden previously said that the U.S. will stand against Russia and support Ukraine's sovereignty.

The Kremlin has yet to release a statement to comment on Putin's phone call with Biden. Officials had said that Putin intends to "normalize" the relations between the two nations to maintain "global security and stability."