Seeking to escalate pressure on Iran, a bipartisan group of senators introduced legislation on Wednesday that would deny the Iranian government access to its foreign exchange reserves parked in the banks of other countries, estimated to be worth as much as $100 billion, mostly in euros.

The legislation, which has strong support, would be the first major new sanction confronting Iran since its inconclusive round of negotiations with the big powers last month on its disputed nuclear program. Despite Iran’s repeated denial, the West suspects it is aiming to be able to build nuclear weapons.

The United States and the European Union have enacted a broad range of economic sanctions aimed at pressuring Iran in those negotiations, but sponsors of the legislation contend that Iran is not bargaining in good faith while it continues to enrich uranium.

Part of the reason, they say, is that Iran has been able to work around the worst effects of the sanctions by tapping its foreign currency reserves overseas, which are largely beyond the reach of current restrictions.