While attention has focused on curbing Iran’s ability to produce fissile material for a nuclear weapon, sanctions, sabotage, technical problems and political calculation have combined to set back Iran’s development of missiles that could potentially deliver such a weapon.

Michael Elleman, an expert on missiles at the International Institute for Strategic Studies, told Al-Monitor in an interview Dec. 16 that the Iranians are “a little bit behind where I thought they would be” in developing missiles with a range beyond 1,500 kilometers (932 miles), and have focused instead on trying to improve the accuracy and lethality of systems with a range of less than 250 kilometers (155 miles).

Elleman credited several factors in slowing Iran’s progress toward longer-range systems. Among them: international efforts to intercept key ingredients — such as aluminum powder for solid propellant fuel; the death in a 2011 explosion of the missile program’s architect, Maj. Gen. Hassan Tehrani Moghaddam, and a dozen of his colleagues; and a likely Iranian desire to avoid provoking the international community by testing longer-range rockets.

Four years ago, Elleman had projected that the Iranians would be able to deploy the Sajjil-2, a two-stage, solid-fuel rocket with a maximum range of about 2,000 kilometers (1,243 miles), by 2013. But the missile, which is produced using Chinese-supplied infrastructure and manufacturing equipment and has been under development for nearly a decade, has not been flight-tested since 2011.