LONDON (Reuters) - Britain is not unquestioning in its support of the United States, defence minister Ben Wallace said on Tuesday, as he underlined the importance of trying to “reboot” the Iranian nuclear deal.

Britain has sought to tread a careful diplomatic line since last week’s killing of a top Iranian general by a U.S. drone strike, avoiding criticising its close ally while also seeking to work with European partners towards a diplomatic solution.

Ministers have said General Qassem Soleimani was a threat but also called for an easing of tensions in the region.

Asked by an opposition Labour lawmaker in parliament about the risks of Britain’s “unquestioning” support of President Donald Trump, Wallace said: “Our support for the United States is not unquestioning at all.”

“We are friends and allies but we are also critical friends and allies when it matters.”

Trump’s administration has said Soleimani was planning new attacks on U.S. interests.

Asked about the legality of the drone strike, Wallace said Britain defended a nation’s right to take such action, and that from the intelligence he had seen “there is a definite case to answer that there would be a cause for self-defence”.

He also said Britain would “call out” any attacks on cultural sites, threatened by Trump but prohibited under international law.

Labour leader Jeremy Corbyn said Prime Minister Boris Johnson’s desire to reach a post-Brexit trade deal with the United States was influencing the government’s judgement.

“Isn’t the truth that he is scared to stand up to President Trump because he has hitched his wagon to the prospect of a toxic Trump trade deal?” Corbyn said in parliament.

“Instead, at this highly dangerous moment, we find the government giving cover and even expressing sympathy for what is widely regarded as an illegal act, because they are in hock to Trump.”

Wallace said Britain was working with Germany and France to “reboot” the 2015 JCPOA Iran nuclear deal, from which Trump unilaterally withdrew the United States in 2018.

“We believe the JCPOA still has life in it ..,” he said, adding that the JCPOA’s dispute resolution mechanism was one route to that end.

“We have not yet gone to that but it is one of the areas you can seek to remedy if you are going to try and pull back Iran from potentially the path that may potentially break that JCPOA.”