BRUSSELS - Representing the United States at a meeting of NATO allies Wednesday, an angry Secretary of State Rex Tillerson dismissed reports that White House officials are pushing him to resign.

Persistent rumours that Tillerson has strained relations with President Donald Trump erupted into headlines last week when US media cited anonymous White House sources claiming that the top diplomat would be gone within weeks.

Tillerson brushed off the reports, but arrived in Europe for talks with EU, NATO and OSCE leaders this week trailed by questions about his future in the job. Asked at NATO talks why he hasn't resigned, he responded firmly. "This is a narrative that keeps coming up every six weeks, and I would say you all need to get some new sources, because your story keeps being wrong," he told reporters.

Trump appointed the 65-year-old former oil executive as Washington's top diplomat in April after receiving recommendations from former top Republican security officials Condoleezza Rice and Bob Gates. He was confirmed easily by the Senate after an illustrious career as chairman of energy giant ExxonMobil, and was initially hailed as an experienced manager with a wealth of international experience and contacts.

But an attempt to slash the State Department budget while reducing staff numbers and streamlining bureaucracy met resistance from career diplomats, and the slow pace of new hires has frustrated some at the White House. There have been reports of rifts with Trump, as well. The president's tweets often appear to undermine Tillerson's diplomatic efforts, such as when Trump said he was "wasting his time" trying to negotiate with North Korea. The State Department was also forced to deny a report that Tillerson had in July branded Trump a "moron" in a private discussion with senior officials at the Pentagon. Then, last week, reports surfaced that he would be replaced before the year's end by CIA director and Trump confidant Mike Pompeo.  Trump has denied this although he did confirm he has had policy differences with Tillerson, tweeting: "I call the shots."

Ukraine peacekeepers are top US priority

Washington's first priority in dealing with the war in Ukraine is to reach agreement on a UN peacekeeping force, US Secretary of State Rex Tillerson said Wednesday.

Speaking a day ahead of planned talks with Russia's Foreign Minister Sergei Lavrov, Tillerson said he hoped to convince Moscow to allow a blue helmet force with a robust mandate. "We prioritise ending the violence, that's our first priority, and to seek to do that we need to put a peacekeeping force in place," Tillerson said.

Russia has brought forward a proposal for a UN force to protect OSCE truce monitors deployed in eastern Ukraine where Russian-backed rebels are fighting Kiev's troops. But Western powers fear that President Vladimir Putin is seeking to limit the force's mandate in such a way that any ceasefire would simply consolidate his allies' gains. "Russia has long resisted a peacekeeping force, but they have agreed now," Tillerson told reporters after talks with NATO allies in Brussels. "I think it's significant that we're talking about the right thing," he said. But he warned that there was a "significant difference" over the mandate the force will have "and that's why we continue to talk with the Russians."

Tillerson is due in Vienna on Thursday for talks with the Organization for Security and Cooperation in Europe and US officials say he is expected to meet Lavrov there. "We hope that we can close those gaps, we think it's vitally important to stop the violence. People are still dying every day," he said. The OSCE has deployed 600 unarmed monitors in Ukraine to investigate and deter ceasefire violations, but they often come under fire from the warring factions.

One observer, an American, was killed in April 2017 in eastern Ukraine when his vehicle hit a landmine.