The United States and Russia have reached an agreement in principle to slash their nuclear weapons stockpiles, the first such pact in nearly two decades. The Wall Street Journal, citing administration and arms control officials, said US and Russian arms control negotiators reached an agreement in principle on the nuclear arms reduction pact. It said the deal, in addition to reducing deployed nuclear weapons, would lower nuclear delivery systems more sharply to between 700 and 800 a side.<br/><br/>It said the breakthrough in the negotiations came two weeks ago when National Security Adviser James Jones and Admiral Michael Mullen, the chairman of the joint chiefs of staff, went to Moscow to overcome stumbling blocks.<br/><br/>The Wall Street Journal said the agreement was approved in principle last week during a telephone conversation between US President Barack Obama and Russian President Dmitry Medvedev. The agreement would mark a breakthrough in months of negotiations to replace the Strategic Arms Reduction Treaty (START), which led to deep cuts in both nuclear arsenals after it was signed in 1991 before the collapse of the Soviet Union.