The mission of experts from the Organization for the Prohibition of Chemical Weapons (OPCW) to probe the use of chemical weapons in Syria’s Douma stalled on Monday amid US accusations against Russia that it meddled with the site of the attack. Russian Defense Ministry official Igor Kirillovdeclared however that the experts will be granted access on Wednesday. "Tomorrow (Tuesday) the security services of the United Nations ... will test the routes. And on Wednesday is when we plan the arrival of the OPCW experts," he told a press conference in the Russian embassy in The Hague, explaining the roads were still being cleared of mines. Washington accused Moscow of blocking the international inspectors from reaching the site of the Douma attack and said Russians or Syrians may have tampered with evidence on the ground. Moscow denied the charge and blamed delays on retaliatory US-led missile strikes on Syria at the weekend. In the fraught aftermath of the suspected attack in Douma and the West’s response, Washington also prepared to increase pressure on Russia, Syrian regime leader Bashar al-Assad’s main ally, with new economic sanctions. European Union foreign ministers threatened similar measures. Syria and Russia deny unleashing poison gas on April 7 during their offensive on Douma, which ended with the recapture of the town that had been the last rebel stronghold near the capital Damascus. Relief organizations say dozens of men, women and children were killed. Footage of young victims foaming at the mouth and weeping in agony has thrust Syria’s civil war — in which half a million people have been killed in the past seven years — to the forefront of world concern again. At least 40 people were killed in the Douma attack. Inspectors from The Hague-based OPCW travelled to Syria last week to inspect the site, but have yet to gain access to Douma, which is now under regime control. “It is our understanding the Russians may have visited the attack site,” US Ambassador Kenneth Ward said at an OPCW meeting in The Hague on Monday. “It is our concern that they may have tampered with it with the intent of thwarting the efforts of the OPCW Fact-Finding Mission to conduct an effective investigation,” he said. His comments at the closed-door meeting were obtained by Reuters. Russian Foreign Minister Sergei Lavrov denied that Moscow had interfered with any evidence. “I can guarantee that Russia has not tampered with the site,” he told the BBC. Britain’s delegation to the OPCW accused Russia and the Assad regime of stopping inspectors from reaching Douma. “Unfettered access is essential,” the British delegation said in a statement. “Russia and Syria must cooperate.” The team aims to collect samples, interview witnesses and document evidence to determine whether banned toxic munitions were used, although it is not permitted to assign blame for the attack. Britain’s Ambassador Peter Wilson said in The Hague that the United Nations had cleared the inspectors to go but they had been unable to reach Douma because Syria and Russia had been unable to guarantee their safety. Moscow blamed the delay on the air strikes, in which the United States, France and Britain targeted what the Pentagon said were three chemical weapons facilities. “We called for an objective investigation. This was at the very beginning after this information [of the attack] appeared. Therefore, allegations of this towards Russia are groundless,” Kremlin spokesman Dmitry Peskov said. OPCW inspectors have been attacked on two previous missions to the sites of chemical weapons attacks in Syria.