The Trump administration has chosen a special envoy for nuclear talks, with the principal task of negotiating a new arms control agreement with Russia and China, according to congressional sources and former officials.

The proposed special negotiator, Marshall Billingslea, is currently the under-secretary for terrorist financing at the US Treasury. His nomination last year for a top human rights job at the state department was stalled by controversy over the extent of his involvement in the torture programme established by the George W Bush administration, in which he oversaw the conditions of detainees in Guantánamo Bay.

Neither the state department nor the treasury responded to a request for comment, but congressional staffers and former officials said Billingslea had accepted the post.

The Trump administration has been trying to recruit a high-level arms control negotiator for several months, but several former Republican officials with significant experience in the field turned down the offer.

Billingslea, who has a long record as a hawk on nuclear weapons issues, faces a daunting task. Donald Trump wants to negotiate a new agreement to reduce the vast nuclear weapons arsenals of the major powers, to replace the New Start deal with Russia agreed by Barack Obama.

Trump wants China to be included in a new agreement but Beijing has so far refused on the grounds that the Chinese arsenal is a small fraction (estimated at about a 20th) of its US and Russian counterparts.

Trump has accepted an invitation from Vladimir Putin to take part in talks on nuclear arms control and other strategic issues at a summit meeting of the five permanent members of the UN security council, most likely at the time of the UN general assembly in September.

One of Billingslea’s tasks would be to prepare for the summit, but in the absence of a major shift by China, he would have to advise Trump on whether or not to extend the New Start deal – the last nuclear arms control agreement to have survived the Trump era – as an interim measure. That is something the president is highly reluctant to do, because the 2010 agreement is part of the Obama legacy Trump has been eager to expunge.

Billingslea is a former aide to the late Republican senator Jesse Helms, who was a fervent opponent of arms control efforts during the cold war, for example blocking US ratification of the Comprehensive Test Ban Treaty, and campaigning for the US withdrawal from the Anti Ballistic Missile treaty.

“No special envoy, especially one like Marshall Billingslea who has a record of dismantling or blocking effective nuclear arms control, can hope to accomplish very much toward the goal of a wholly new multilateral nuclear arms control agreement through a one-day heads of state summit,” said Daryl Kimball, executive director of the Arms Control Association. “But a decision by Trump and Putin to extend the New Start agreement would surely help prevent a new arms race and create more favorable conditions for more ambitious nuclear arms talks with Russia and China.”

Alexandra Bell, senior policy director at the Center for Arms Control and Non-Proliferation, said: “Now that he has been selected, Mr Billingslea has no time to lose. In less than a year, we could lose the last major treaty constraining the world’s two largest nuclear arsenals.”