The Pentagon says it won’t be making more weapons, and it won\’t make any more missiles, as part of an agreement with Russia

WASHINGTON — The Pentagon said Wednesday it will not be making any more weapons of mass destruction or advanced cruise missiles for its new $500 billion defense spending plan, but will continue to buy a limited number of long-range missile defense systems.

The Pentagon and Russian Defense Minister Sergei Shoigu announced their agreement on Wednesday after months of talks, with the first of the new systems to be delivered in 2021.

The Pentagon has said that if Russia’s new systems are deployed on American and allied aircraft carriers and warships, the United States will be able to use its nuclear arsenal to defend against an attack by Iran and its allies.

But that option has not been part of the $500-billion Defense Department plan, which is a major defense program.

Under the pact, the Pentagon will buy the new Russian systems in 2021 for about $2.2 billion each.

The plan calls for the Pentagon to buy at least $3.5 billion in medium-range ballistic missiles and possibly another $5 billion for ballistic missile defense batteries.

The deal with Russia was reached on the eve of the 10th anniversary of the September 11, 2001, terrorist attacks, and is aimed at bolstering the U.S. and its NATO allies against a resurgent Iran, which has pursued nuclear weapons and ballistic missile technology.

“The United States and Russia are working together to increase our security capabilities and to address some of the challenges that confront us in the 21st century,” Defense Secretary Ash Carter said at a news conference.

“This agreement will help protect our interests and our allies, and the defense budget will be better able to do so.”

The agreement with Russian officials comes as tensions between the United Kingdom and Russia have escalated in recent weeks.

Britain announced Wednesday it would cancel plans to send a naval warship to join a Russian naval exercise in the Black Sea, saying it will send only a few ships to the exercises.

Russia said it would send only about 200 sailors to the drill.

Meanwhile, the U-boat threat to the Baltic states has grown, and in recent days the U.-S.

naval command said a Russian submarine has been detected off the coast of Estonia, and a Russian warship was detected off Sweden.

The Russian Navy has warned that it will respond to any U.s. or NATO ships entering its waters.

In recent weeks, U.N. Secretary-General Antonio Guterres has called for a cease-fire in the conflict in Ukraine, which he says is a violation of the 1991 Budapest Memorandum, which calls for a de-escalation of the conflict.