BRUSSELS (Reuters) - While European powers France and Britain are lobbying Washington to cool tensions since North Korea s most powerful nuclear test a month ago, EU nations with embassies in Pyongyang are directly pressing the North Koreans.   A group of seven European Union countries - the Czech Republic, Sweden, Poland, Romania and Bulgaria, as well as Britain and Germany - held at least two formal meetings with North Korean officials in Pyongyang in September, three EU diplomats said.  But they felt frustrated because the higher-level access that they had obtained in Pyongyang last year had fallen away, with only medium-ranking foreign ministry officials now attending the meetings, the diplomats said.  There was a sense that we weren t really getting anywhere because they sent these department heads,  said a Brussels-based diplomat who had been briefed on the meetings, which were described as  very serious  in atmosphere and tone.   They want to talk to the United States.  The White House has ruled out such talks, with President Donald Trump telling Secretary of State Rex Tillerson he would be  wasting his time  negotiating with the North Koreans. The United States has no embassy in Pyongyang and relies on Sweden, the so-called U.S. protecting power there, to do consular work, especially when Westerners get into trouble.  In contrast to recent meetings, when North Korean officials met EU envoys in the Czech Republic s embassy in 2016 to discuss issues including cultural programs and regional security, a deputy foreign minister would attend, one EU diplomat said.  For the small club of European Union governments with embassies in North Korea, that reflects Pyongyang s anger at the EU s gradually expanding sanctions that go beyond those agreed by the United Nations Security Council.  It could have repercussions for broader EU efforts to help mediate in the nuclear crisis, according to the EU diplomats briefed by their colleagues in Pyongyang, as the bloc prepares more measures against North Korea. EU foreign policy chief Federica Mogherini, who chaired talks on the historic 2015 nuclear deal with Iran, says the bloc is ready to mediate in any talks aimed at freezing North Korea s missile and nuclear weapons programs. But at the same time, the European Union wants an oil embargo on Pyongyang that it hopes other countries will follow.  Some EU governments are pushing to cancel North Korean work permits in Poland and other eastern European countries because EU officials believe workers  salaries are deposited in bank accounts controlled by the regime in Pyongyang.  The North Koreans are starting to see the EU as a U.S. puppet, but we stress that we are an honest broker,  said a second EU diplomat.  Links with the EU embassies go back years. Communist Czechoslovakia was a leading supplier of heavy machinery to North Korea. As a Soviet satellite, Czechoslovakia established diplomatic ties with North Korea in 1948, along with Poland and Romania.  The seven European embassies in Pyongyang are among only 24 foreign missions there, including Russia, China and Cuba. The EU s status as a potential broker relies, in part, on Sweden, which was the first Western European nation to establish diplomatic relations with the North in 1973. Sweden is a member of the Neutral Nations Supervisory Commission, which was set up to oversee the 1953 armistice between North and South Korea, undertake inspections, observe military exercises and promote trust between the two sides. Czechoslovakia was also a member of the Neutral Nations Supervisory Commission until the early 1990s.  Sweden played a key role in the release of Canadian pastor Hyeon Soo Lim and of U.S. student Otto Warmbier earlier this year. But Sweden has strongly backed the EU sanctions.  The seven European embassies are limited in what they can say because North Korean staff, required by the government to work at the EU embassies, are expected to double as informants for Pyongyang, the diplomats said.  Sanctions and pressure ... Sadly, we don t have anything else,  said an EU diplomat in Brussels. The joint meetings with the North Koreans, usually held at a single European mission, have been focused on the release of imprisoned Westerners, not big diplomatic initiatives. But as efforts intensify to calm U.S. and North Korean threats of war, they could still prove an important channel to pass messages between Pyongyang and Washington.  In the best case, we could perhaps facilitate an opening of a diplomatic track between the North Koreans and the United States,  said Carl Bildt, a former Swedish prime minister and foreign minister from 2006 to 2014. Bildt said anything the EU does must be kept secret.  If the EU does something along these lines, the first thing the EU should do is not to talk about it. Talking about it is a pretty good way to ensure that one can t do it,  he said. Mathieu Duchatel, a North Korea expert at the European Council on Foreign Relations, a think-tank that Bildt also now helps oversee, said the European Union could chair talks between China and the United States. Washington and Pyongyang have no hotlines to prevent crises from spinning out of control and it is not clear what Beijing s reaction would be if the United States intercepted a North Korean missile test, Duchatel said. For now, Paris is in contact with White House National Security Adviser H.R. McMaster and White House Chief of Staff John Kelly, diplomats said, noting French President Emmanuel Macron s budding relationship with U.S. President Donald Trump.  Lieutenant General McMaster and Kelly, a retired four-star Marine Corps general, have a soft spot for France born of their admiration for the French military, the diplomats said. It is unclear if that translates into a direct impact on Trump s thinking on North Korea, European diplomats said.  They are trying to normalize Trump, but I don t think Trump can be normalized,  said a senior French diplomat.  To get him to listen, heads of state need to speak to him directly.  Macron, who has ruled out a military option, has said he believes he could convince Trump to avoid armed intervention. Macron s position is to keep repeating the mantra of patience and dialogue to Trump, diplomats said. 