The White House announced Thursday that Biden has proposed a five-year extension of the New START treaty to Russia, which the Kremlin welcomes. https://www.foxnews.com/politics/biden-giving-putin-wanted-nuclear-arms-treaty-cotton

1. New START (Strategic Arms Reduction Treaty) "reduction of strategic offensive arms") is a nuclear arms reduction treaty between the United States and the Russian Federation with the formal name of Measures for the Further Reduction and Limitation of Strategic Offensive Arms.

2. It was signed on 8 April 2010 in Prague, and, after ratification, entered into force on 5 February 2011. It is expected to last at least until 2021.
The treaty calls for halving the number of strategic nuclear missile launchers. A new inspection and verification regime will

3. be established, replacing the SORT mechanism. It does not limit the number of operationally inactive nuclear warheads stockpiled by Russia and the United States, a number in the high thousands.

4. "This is a very bad decision," Cotton told host Martha MacCallum. "It puts America's national security at risk. The new START treaty is a one-sided treaty that favors Russia."
The Trump administration had waited until last year to begin talks

5. on prolonging the pact, and included a list of demands Russia would not meet. "We are at the risk of facing nuclear overmatch by the combined nuclear forces of Russia and China, and it was a terrible decision of the Biden administration

6. to fold their cards and give Vladimir Putin exactly what he wanted on their very first day in office." Cotton said.

Sources: Wikipedia, Fox News