By Michael R. Gordon and Eric Schmitt WASHINGTON: Russia has sent a military advance team to Syria and is taking other steps the United States fears may signal that President Vladimir Putin is planning to vastly expand his military support for President Bashar Assad of Syria, administration officials said Friday. The Russian moves, including the recent transport of prefabricated housing units for hundreds of people to a Syrian airfield and the delivery of a portable air traffic control station there, are another complicating factor in Secretary of State John Kerry’s repeated efforts to enlist Putin’s support for a diplomatic solution to the bloody conflict in Syria. The Russians have also filed military overflight requests with neighboring countries through September. US officials acknowledge that they are not certain of Russia’s intentions, but some say the temporary housing suggests that Russia could deploy as many as 1,000 advisers or other military personnel to the airfield near the Assad family’s ancestral home. The airfield serves Latakia, Syria’s principal port city. Other US officials say they see no indication that Russia intends to deploy significant numbers of ground forces, but they say the housing would enable Russia to use the airfield as a major hub for ferrying in military supplies for the Syrian government or possibly as a launch pad for Russian airstrikes in support of Assad’s forces. US intelligence analysts are also looking at ship loadings in Russia to determine what might be bound for Syria, and one official speculated that the Russian deployment might eventually grow to 2,000 to 3,000 personnel. “There are some worrisome movements — logistical, preparatory types of things,” said an administration official, who added that there was no confirmation that large numbers of Russian soldiers, aircraft or heavy weapons had yet arrived. Officials asked for anonymity because they were discussing classified intelligence reports. Syria is one of Russia’s major arms clients and is also host to a Russian naval base at the port city Tartus. But the new concerns from intelligence analysts, as well as news and social media reports in the Middle East, led to warnings this week from the State Department and White House about Putin’s intentions. “We have regularly and repeatedly expressed our concern about Russian military support for the Assad regime,” said John Kirby, the State Department spokesman. “But we’re also watching their actions very carefully. If these reports are borne out, it would represent a very serious shift in the trajectory of the Syria conflict and call into question any Russian commitment to a peaceful settlement.” Kerry flew to Sochi, Russia, in May to meet with Putin to explore whether the two sides could cooperate on Syria. In August, Kerry followed up with an unusual three-way meeting in Qatar on the Syria crisis with Sergey Lavrov, the Russian foreign minister, and their Saudi counterpart, Adel al-Jubeir. Stepped-up Russian military support for the Syrian government could pose a problem for the United States in several ways. If Putin’s intention is to support not just the Syrian government but also Assad, that could undercut Kerry’s contention that the Syrian president needs to leave power as part of any political solution to the conflict. And if Russian pilots carried out airstrikes, administration officials say, the choice of targets might further aggravate the growing chaos. Russian strikes on Islamic State militants could interfere with, or at least complicate, the air operations that the US-led coalition is already conducting in Syria against the group. But if Russia targets rebel groups that are opposed to Assad, they might be striking some of the moderate Syrian fighters who have been trained by the CIA and the Pentagon. Another possibility is that Russia is taking these steps to secure its own interests in the event that the Assad government collapses, reaches a power-sharing agreement with the opposition or is replaced. By expanding its military influence in Syria, Russia might be in a stronger position to shape the political outcome as the Assad government’s military position weakens by encouraging it to share power with opposition members Moscow supports. It is not clear if the Obama administration has pressed the Russian government on its intentions, although some officials said such a discussion was likely in the coming days. On Friday in Vladivostok, Russia, Putin dismissed news reports that Russia had sent ground troops to fight in Syria as “premature.” “We are looking at various options, but so far what you are talking about is not on the agenda,” he said at a news conference at the Eastern Economic Forum. But Putin said Russia was supplying arms to the Assad government under contracts that go back five to seven years and suggested that the Syrian authorities should be part of a new international alliance against terrorism. “We have already lent serious support to Syria with our equipment, with training soldiers, with our weapons,” he added. “We really want to create some type of international coalition to fight terrorism and extremism.” Outlining his ideas on a potential diplomatic solution, Putin suggested that it be carried out in parallel with the fight against extremists and that Assad should play a role in the political process. “The Syrian president, as a matter of fact, agrees with that, including holding early elections, parliamentary elections, and establishing contact with the so-called ‘healthy’ opposition, bringing them into governing,” Putin said. He did not elaborate on which opposition should be considered “healthy,” although Moscow has periodically been at odds with the main exile opposition group supported by Western governments. Saudi Arabia’s foreign minister, al-Jubeir, who accompanied the Saudi king to Washington for a meeting at the White House on Friday, said his country was trying to confirm whether the Russians had offered direct military assistance to Syria. But he expressed alarm over the prospect. “If true, this would represent a serious escalation and a very dangerous escalation,” al-Jubeir said at a news conference in Washington. Jeffrey White, a former Defense Intelligence Agency officer who now studies Syria at the Washington Institute for Near East Policy, said that Putin’s intentions were clear. “All this tells me is that the Russians are not backing away from the Assad regime,” he said.