The Wall Street Journal has reported that inside the transition office of US President-elect Donald Trump, advisers have offered multiple proposals to end the war in Ukraine.

Trump has yet to specify how he will end Russia's invasion of Ukraine, despite his pledge to do so.

The US newspaper quoted sources close to Trump as saying that all the proposals break from President Joe Biden's approach of letting Ukraine dictate when peace talks should begin.

The proposals uniformly recommend freezing the war in place -- cementing Russia's seizure of roughly 20 percent of Ukraine -- and forcing Ukraine to temporarily suspend its quest to join the North Atlantic Treaty Organization.

One idea proposed would involve Ukraine promising not to join NATO for at least 20 years. In exchange, the US would continue to supply Ukraine with weapons to deter a future Russian attack.

Under this plan, the front line would essentially be locked in place and both sides would agree to an 800-mile or roughly 1,200 kilometer demilitarized zone.

The newspaper also reported that Trump has not approved a specific peace plan, and quoted sources as saying that while advisers have offered ideas, only the president-elect will decide how to handle the matter.

The paper pointed out that if the US reveals a plan that forces Ukraine to negotiate, its public would view ceding territory as capitulation to Moscow. It added that there will be stiff resistance from some NATO allies.