The days are gone when nuclear weapons reduction talks between Moscow and Washington were the biggest and most important diplomatic game on earth, but this is still a treaty of huge significance. It contains new lower limits on the number of warheads the two sides can deploy and on the missiles, submarines and bombers which carry them. For Barack Obama who has spoken of the dream of a non-nuclear world, it also sends a powerful signal on the key contemporary issue. The White House believes US efforts to prevent Iran and North Korea acquiring nuclear weapons will be enhanced if it's seen to be reducing its own arsenal.

The Israeli military says that two of its soldiers have been killed and two others injured in clashes with Palestinian fighters in the southern Gaza Strip. Israel said two Palestinians who were planting explosives on the border were also killed. Our Middle East correspondent Jon Donnison reports from Jerusalem.

These clashes came around in an attempt by militant groups in Gaza to capture another Israeli soldier to add to Gilad Shalit who's now been held for more than three years. Local sources in Gaza say fighting broke out after an Israeli incursion into the southern Gaza Strip. Such incursions are relatively frequent in this area. It appears that militants in Gaza then tried to capture at least one Israeli soldier. The militant wing of Hamas has claimed responsibility for the deaths of the two Israeli soldiers, but says it was a defensive action.