Protecting the vastness of the U.S. demands very different capabilities than those of Iron Dome, which has successfully shot down rockets and missiles using ground-based interceptors.

"high level" talks are taking place with the US about joining its proposed "Golden Dome" missile defence system, aimed at countering futuristic threats.

Major stock indexes and the dollar fell on Wednesday as investors worried about a deteriorating U.S. fiscal outlook and Treasury yields climbed following a poorly received sale of 20-year U.S. bonds.