Qatar on Monday demanded neighbouring oil-rich Gulf states — namely Saudi Arabia, the United Arab Emirates (UAE) and Bahrain — lift their “blockade” of the emirate as a pre-condition for crisis talks. Meanwhile, the UAE warned that Doha's isolation could last years, and US President Donald Trump's administration continued to send mixed signals on where it stands. Qatar's Foreign Minister Sheikh Mohamed Bin Abdel-Rahman Al-Thani called measures imposed against Doha by Gulf neighbouring countries and Egypt “an act of aggression”. “We have to make it very clear for everyone, negotiations must be done in a civilised way and should have a solid basis and not under pressure or under blockade,” he told reporters in Doha. “Qatar under blockade — there is no negotiation. They have to lift the blockade,” said Sheikh Mohamed ahead of a scheduled visit to Washington this week in which he was due to hold meetings with senior US officials. “Until now we didn't see any progress about lifting the blockade, which is the pre-condition for anything to move forward.” On 5 June, Saudi Arabia and its allies cut all diplomatic ties with Qatar, pulling their ambassadors from the gas-rich emirate and giving its citizens a two-week deadline to leave their territory. While Egypt strongly supported the Saudi and Gulf measures, it did not ask Qatari citizens to leave, considering that nearly 300,000 Egyptians work in Qatar. The tiny Gulf state also maintains huge investments in Egypt. The measures also included closing Qatar's only land border, banning its planes from using their airspace and barring Qatari nationals from transiting through their airports. The only land border Qatar maintains is with Saudi Arabia, and Doha had to seek help from Turkey, Iran, Morocco and other nations to make up for the shortage in food and other basic products. Saudi Arabia, the UAE, Egypt, Bahrain and others accuse Qatar of supporting and funding “terrorism” and of working with regional rival Iran — charges Doha firmly denies. Asked if the ultimate aim of the Gulf countries was to enforce regime change, the Qatari foreign minister replied: “No one is in a position of imposing regime change in this country. Our system here is based on a consensus between the people and its ruler.” Sheikh Mohamed's demand came as a UAE state minister for foreign affairs warned Qatar's diplomatic isolation could “last years”. “We do not want to escalate, we want to isolate,” UAE State Minister for Foreign Affairs Anwar Gargash told journalists in Paris. “This isolation can take years.” Gargash said that while Qatar's rivals were “betting on time”, a solution could not be brokered until it abandoned its support for “extremist Islamists”. “They have built a sophisticated podium for jihadism and Islamic extremism,” he said. “They support groups linked to Al-Qaeda in Syria, Libya... and in Yemen. This state is weaponising jihadists and Islamists; it is using this as a weapon of influence,” he added. Qatar's Sheikh Mohamed said Doha had not received any demands from the Gulf states, or from countries seeking a diplomatic solution, including Kuwait, the United States, France and Britain, as the conflict dragged into its third week. “Why they didn't submit their demands yet? For us, there is no clear answer for this,” he said. “But what we have seen until now, there is no solid ground for these demands, that's why they didn't submit their demands yet.” The foreign minister said the economic impact on Qatar had so far proved to be minimal, but added: “We are not claiming we are living in a perfect condition.” On Monday, Youssef Mohamed Al-Jaida, chief executive of the Qatar Financial Centre, said the “blockade” had put at risk business deals worth $2 billion in Arab countries that have cut ties with Doha. Qatari, Saudi and UAE foreign ministers have been crossing paths while touring European capitals, namely Britain, France and Germany, and the United States in order to win the support of their governments for their stances. However, the country with most influence over all oil-rich Gulf nations, the United States, remained ambiguous on where it stands. While President Trump maintained a hard line against Doha, described Saudi King Salman as a “friend” and pressed Qatar to “stop its funding of terrorism”, State Department and Pentagon senior officials maintained a softer line, and even continued business as usual in terms of military cooperation. On 14 June, Washington and Doha announced that they have finalised a $12 billion arms deal to provide Qatar with 36 F-15 fighter jets. The deal was in the works for a while, and is part of a larger $21 billion agreement made back in November 2016, in the waning weeks of the Obama administration. US Defense Secretary James Mattis signed the deal with his Qatari counterpart in the middle of the escalating crisis with Saudi Arabia, so that contracting procedures could start. Mattis also praised joint military exercises that were concluded Friday between the two countries in Qatar's territorial waters. “The mixed messages the administration is sending on many national security issues is baffling,” Senator Tim Kaine (D-VA), a member of the Armed Services and Foreign Relations Committees, said. Qatar hosts the vitally important Al-Udeid airbase, where some 10,000 US troops reside. It's a vital base in the US fight against the Islamic State group, and that's likely why US defence officials have a different view of Qatar's utility. Turkish troops also arrived in Qatar early this week to take part in joint training exercises. The first drills took place Sunday at the Tariq Bin Ziyad military base in Doha, the Qatari Defence Ministry said in a statement. Turkey, one of Qatar's strongest allies, has offered to mediate an end to the conflict with Saudi Arabia in particular, considering the vital economic interests shared between Ankara and Riyadh. France, Morocco and Sudan have also offered to act as mediators. All three countries have vital financial interests with Doha. Turkish President Recep Tayyip Erdogan is known for his sympathy with the Muslim Brotherhood group, which receives strong backing from Doha, and that has been one of the key reasons listed by Gulf nations and Egypt for severing ties with Qatar. Erdogan, has been outspoken in his support for the Qatari cause, condemning the Saudi-led blockade as “almost like a death sentence” for Qatar. “Qatar is not the one who supports terrorism, quite the opposite,” he said last week. “Along with Turkey, it is the country with the most resolute stance against [the Islamic State group] which has caused grave damage to our region.” Qatar's Sheikh Mohamed also warned that the Gulf political crisis has affected countries outside the region. “France, UK or the United States — they are strong allies of Qatar and we have a great deal of cooperation together in terms of military, defence, security, economically,” he said. “So a blockade on Qatar, and measures being taken against Qatar in this way, affects the interests of those countries as well, directly.” Concern over the ongoing crisis also surfaced at a meeting of European Union foreign ministers in Luxembourg on Monday, who said “the depth of the crisis is more worrying than at any time before”. EU Foreign Affairs Chief Federica Mogherini called for “de-escalation” and encouraged “all Gulf countries to engage in political dialogue without preconditions”. Experts fear the crisis could draw in other countries. Amnesty International has flagged the humanitarian cost of the crisis, warning it was “spreading fear” across the region. Saudi Arabia, the UAE and Bahrain had given their citizens until 19 June to leave Qatar, a deadline that was reached Monday.