Pakistan’s nuclear arsenal now totals more than 100 deployed weapons, a doubling of its stockpile over the past several years in one of the world’s most unstable regions, according to estimates by nongovernment analysts.

The Pakistanis have significantly accelerated production of uranium and plutonium for bombs and developed new weapons to deliver them. After years of approximate weapons parity, experts said, Pakistan has now edged ahead of India, its nuclear-armed rival.

An escalation of the arms race in South Asia poses a dilemma for the Obama administration, which has worked to improve its economic, political and defense ties with India while seeking to deepen its relationship with Pakistan as a crucial component of its Afghanistan war strategy.

In politically fragile Pakistan, the administration is caught between fears of proliferation or possible terrorist attempts to seize nuclear materials and Pakistani suspicions that the United States aims to control or limit its weapons program and favors India.

Those suspicions were on public display last week at the opening session of U.N. disarmament talks in Geneva, where Pakistani Ambassador Zamir Akram accused the United States and other major powers of “double standards and discrimination” for pushing a global treaty banning all future production of weapons-grade uranium and plutonium.

Adoption of what is known as the “fissile materials cutoff treaty,” a key element of President Barack Obama’s worldwide non-proliferation agenda, requires international consensus. Pakistan has long been the lone holdout.

While Pakistan has produced more nuclear-armed weapons, India is believed to have larger existing stockpiles of such fissile material for future weapons. That long-term Indian advantage, Pakistan has charged, was further enhanced by a 2008 U.S.-India civil nuclear cooperation agreement.

Brig. Gen. Nazir Butt, defense attache at the Pakistani Embassy in Washington, said the number of Pakistan’s weapons and the status of its production facilities were confidential.