A South Korean watches news reporting about a nuclear test conducted by North Korea on a TV screen in Seoul, South Korea. With China’s backing, the U.S. has proposed tough new sanctions aimed at missiles and nuclear technology. (Lee Jin-man/AP)

Backed by China, the United States introduced a U.N. resolution Tuesday that would impose fresh financial and diplomatic sanctions on North Korea and tighten measures aimed at preventing Pyongyang from importing or exporting technology for its nuclear or ballistic missile programs.

The United States proposed the new round of sanctions in a draft resolution three weeks after North Korea conducted its third, and most advanced, nuclear test.

China’s public support for the move underscored its displeasure with its unpredictable neighbor, which has repeatedly dismissed Beijing’s appeals to halt its nuclear tests. But at China’s insistence, the sanctions were crafted to impede North Korea’s nuclear and ballistic missile programs without blocking its legal trade.

Susan E. Rice, the U.S. ambassador to the United Nations, circulated the draft resolution to the Security Council’s 15 members, ending weeks of closely guarded negotiations with China’s U.N. envoy, Li Baodong. The draft condemns North Korea’s nuclear and missile programs and would impose new restrictions on banks conducting business with Pyongyang.

The latest proposal would be the fourth round of sanctions imposed on North Korea in an attempt to rein in its nuclear ambitions. Rice called the sanctions “some of the toughest” ever imposed by the United Nations.

With the support of China, the North’s strongest ally, the sanctions could be adopted later this week. All 15 members of the Security Council condemned the latest nuclear test on Feb. 12.

Rice told reporters the new resolution would reinforce existing financial sanctions, target “illicit activities” of North Korean diplomats and banks, and expand travel restrictions on individuals linked to North Korea’s banned programs.

The resolution would also add the names of three suspected North Korean arms traffickers and two North Korean companies allegedly involved in the country’s ballistic missile or nuclear program. It would increase pressure on countries to search suspect ships for illegal cargo and strengthen a ban on the import of luxury goods by North Korea, including yachts, automobiles, some jewelry and racing cars. In addition, it would urge governments to exercise vigilance in monitoring suspected illegal activities by North Korean diplomats.

“The sanctions contained in this draft resolution will significantly impede North Korea’s ability to develop further its illicit nuclear and ballistic missile programs” and increase the cost of defiance, Rice said. “It builds upon, strengthens and significantly expands the scope of the strong U.N. sanctions already in place.”

China’s U.N. envoy said a “strong signal must be sent out that nuclear tests” go against the will of the international community.

North Korea’s public response has been belligerent, threatening military action against the United States. On Tuesday, North Korea threatened to nullify the 1953 armistice agreement ending the Korean War in response to sanctions, South Korea’s Yonhap news agency reported.