The report by the Norwegian Refugee Council and International Rescue Committee noted the "substantial and generous hospitality" of Lebanon, Jordan, Iraq and Turkey to accept three million Syrians.
But it said they were struggling to cope and had imposed stringent controls that have "dramatically" stemmed the inflow of refugees from the devastating war that broke out in 2011.
The report titled "No Escape" also criticised Western countries for failing to resettle an adequate number of Syrians stranded in the Middle East.
"In the context of increasing humanitarian needs within Syria and in neighbouring countries, legitimate national security concerns and insufficient international support, the formal and informal border crossings out of Syria are now effectively closed to men, women and children seeking safety," said the report.
In recent weeks, Lebanon has all but shut its frontiers to new refugees, allowing only humanitarian exceptions across, while Jordan and Turkey frequently place restrictions on their entry, it added.
As a result, and in spite of the Syrian civil war showing no signs of abating, "the overall number of refugees leaving the country has decreased dramatically" in the past few months.
In 2013, the United Nations estimated that an average of 150,000 refugees were registered each month leaving Syria.
"In October 2014, the figure was only 18,453, representing an 88-percent drop from the 2013 monthly average," said the report.
LIVING IN CONSTANT FEAR
But the report criticised countries further afield, especially in the West, for failing to resettle some of the refugees to ease the burden on those near Syria.
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"Countries not sharing borders with Syria have shown a remarkable lack of solidarity both with Syria's civilian population seeking to escape violence and with the neighbouring countries that host the overwhelming majority of refugees," said the report.
Lebanon is home to the highest refugee population per capita in the world.
In September and October this year, Turkey received 190,000 refugees, "far more than the entire international community has committed to resettle since the start of the Syrian conflict", the report said.
On the other hand, France had pledged to resettle "a mere 500 refugees from Syria, while the UK has said it will only take a few hundred".
"The United States also needs to do more, and do it more quickly," the report said.
"Resettlement... alone cannot solve the refugee crisis.
"However, combined with a fully financed humanitarian response (currently only 47 percent funded) and development support... to host governments, offering to resettle significant numbers of people outside the region will go some way to help relieve the suffering."
Refugees living in Syria's neighbouring countries meanwhile face daily, often insurmountable challenges.
The report cites the case of Hassan, a 55-year-old father who entered Lebanon with his family across an unofficial frontier crossing.
Because of this, "Hassan lives in constant fear of arrest and deportation" and was unable to seek the healthcare he needs for his son because he is terrified of being caught at a checkpoint.