Russia may be withholding vital information about the whereabouts of the fugitive Bosnian Serb general and genocide suspect, Ratko Mladić, who faces war crimes charges in The Hague, senior Serbian government officials have privately told American diplomats in Belgrade.

In discussions detailed in a diplomatic cable marked "secret" and sent to Washington by US chargée d'affaires Jennifer Brush in September 2009, Miki [Miodrag] Rakić, chief of staff to the Serbian president, Boris Tadić, tells Brush it remains likely Mladić is hiding somewhere in Serbia.

But Rakić also suggests the fugitive is being assisted by "foreign sources" and hints darkly that Moscow may have better information about Mladić's exact situation than does the Serbian government.

"Russia has not been forthcoming on Serbia's requests for assistance in locating Hague indictee Mladić, presidential adviser Miki Rakić told us on August 25 [2009]," says the American cable, which has been released by WikiLeaks.

Given the frustration with the lack of Russian help, Tadić was expected to raise the Mladić issue with Russia's president, Dmitry Medvedev, adds Rakić - who heads Serbia's intelligence-based Mladić manhunt.

"Asking that the information 'remain at this table', Rakić told us that he had posed a series of questions about specific contacts between Mladić associates and Russian diplomats, as well as 'phone calls and trips to Russia by Mladić associates'."

Rakić said he had addressed his inquiries to the Russian federal security service (FSB) director, Aleksandr Bortnikov, Russian national security adviser, Nikolai Patrushev, and Medvedev's chief of staff, Vladislav Surkov – but had not received replies from any of them.

"If the Russians did not respond before Medvedev's visit, Rakić said, Tadić would raise the issue himself," Brush's cable reported.

Medvedev visited Belgrade in October 2009 to sign a raft of bilateral loan and co-operation agreements on energy, education and security. If Tadić raised the Mladić case with him, neither man said so in public.

Previous unconfirmed reports have suggested that Mladić may have found sanctuary in Russia as pressure grew on Serbia to arrest him.

Although prosecutors in The Hague believe Mladić to be in Belgrade, Serbian officials say they have had no firm information on his whereabouts since 2006, a time when, according to the diplomatic traffic, the US embassy in Belgrade was withering about Belgrade's half-hearted attempts to arrest Mladić.

The Americans have given greater credence to the Serbian efforts in the past two years, although top European politicians remain sceptical.

In July 2009, state department officials discussed the Mladić case with the Dutch government in Washington.

"Serbian leaders say one thing in person, another to the international press, and another to their own publics," Maxime Verhagen, the then Dutch foreign minister, told Philip Gordon, the US assistant secretary of state for European affairs .

The same cable reveals that the Americans had just sent a team of FBI experts in "fugitive recovery" to Belgrade to help the manhunt and assess the Serbian operations.

Belgrade embassy cables going back to 2006 disclose that the Americans also sent US marshals to Serbia and proposed an 11-point plan to the Serbian government which was comprehensively snubbed. The former Serbian prime minister, Vojislav Koštunica, is singled out for blame.

"The US government provided the government of Serbia with 11 recommendations designed to advance the hunt for Ratko Mladić," wrote then US ambassador, Michael Polt, in October 2006. "Due primarily to the resistance of Prime Minister Koštunica himself, the government has not carried out in full a single one of our recommendations."

The Russian authorities have been sheltering several of the most wanted people in Serbia for years. Mladić and Goran Hadžić, a leader of Croatian Serbs during the 1991-95 war, are the last Serbian war crimes suspects wanted by the international tribunal in The Hague. Hadžić has also been reported to be in Russia.

Mirjana Marković, the widow of the late Serbian leader, Slobodan Milosević, and her son, Marko Milosević, have both been protected in Russia for years despite being sought by Belgrade on fraud and embezzlement charges and in connection with the murder of a Serbian journalist. An Interpol arrest warrant for Marko is ignored by the Russians.

Other secret American cables in the 2009-2010 period also focus on Mladić and his fellow Hague indictee, Hadžić, stressing how important their capture is to Serbia's bid to join the European Union.

Senior officials tell the Americans they are doing all they can and some, contradicting Rakić, suggest Mladić is no longer in Serbia. Sooner or later in the course of these discussions, the Russian connection resurfaces.

In a cable dated May 2009 the US embassy in Belgrade discusses whether Serbian leaders could do more to apprehend Mladić – and concludes that, unlike their predecessors, they were doing as much as they could.

"The current government clearly wants to find Mladić, a prerequisite for moving ahead with EU accession," it says. One proof of this contention, according to quoted officials, is that chief of staff Rakić was leading meetings of the action team, indicating that the hunt for Mladić "was a personal priority of President Tadić".

All the American diplomatic reporting in this period takes place in the context of a struggle between the US and Russia for influence over Serbia's future direction. Medvedev's visit to Belgrade is seen very much as part of this contest for influence, following as it does US vice-president Joe Biden's visit in May 2009, which the Americans judge to be "a new beginning". But the US faces an uphill fight in a country that was bombed by Nato little more than a decade ago – and which still feels great affinity for Russia. "We still have a great deal of work to do to uproot entrenched stereotypes of the US government as imperialistic, anti-Serb and pro-Albanian," chargée d'affaires Brush writes in a cable posted in July 2009.

"Frequent statements from the Serbian government characterising the United States as an international bully, combined with a pronounced aversion to acknowledging US partnership and assistance and a penchant for exaggerating Russian contributions … contribute to this outdated public perception. We will push our Serbian interlocutors to take a more balanced and mature approach."