A man smokes next to a street cart selling tea Tuesday at the closed Turkish border gate in Kilis. Turkish officials say about 30,000 refugees have massed at the border after fleeing Russian airstrikes and a regime offensive surrounding the city of Aleppo . (Chris Mcgrath/Getty Images)

Turkey angrily rejected demands Wednesday that it open its border to tens of thousands of Syrian refugees driven from their homes by relentless Russian airstrikes, saying that to do so would amount to complicity in the Russian-backed offensive to drive rebels out of the province of Aleppo.

The blunt acknowledgment that politics are part of the calculus in this latest humanitarian crisis in Syria underscores the dilemma confronting Turkey as it grapples with the prospect of a new refugee influx as well as the fear that hostile forces­ will overrun territory adjoining its border.

It was a reminder, too, of the ways in which civilians have routinely become pawns in the Syrian conflict, which has already displaced more than half the pre­war population and created a vast diaspora of nearly 5.5 million refugees beyond Syria’s borders.

The numbers could soon increase significantly if the Syrian government achieves its stated goal of encircling and eventually recapturing the provincial capital of Aleppo, Syria’s largest city. Half of the city and much of the countryside have been under rebel control since 2012, but the intervention of Russia’s air force in September tilted the balance of power on the ground in favor of President Bashar al-Assad.

An offensive launched last week has succeeded already in severing a vital rebel supply route between the Turkish border and the rebel-held portion of Aleppo city, and also torpedoed fragile peace talks in Geneva that were suspended before they had begun. More than 500 people have been killed in the nine days since the battle began, many of them in the heavy Russian airstrikes that preceded the government loyalists’ advances­ on the ground, according to the Britain-based Syrian Observatory for Human Rights.

World powers are scheduled to meet in Munich on Thursday in an effort to salvage the peace process, but the intensified fighting has given little reason to hope that a breakthrough is near.

More than 50,000 people have fled the latest fighting, according to the International Committee of the Red Cross. The Turkish government said that more than 70,000 and up to 100,000 have been displaced by the battles and that as many as 600,000 could eventually flee the Aleppo region.

About 30,000 people have converged on the Turkish border in the past week to escape the new offensive. They have gathered at the Bab al-Salameh border crossing on the Syrian side just south of the Turkish city of Kilis. There they are being aided by the Turkish relief agency IHH, which has been shipping tents and meals across the border.

But some still are sleeping in muddy fields in temperatures that drop below zero at night, and conditions are miserable even for those sheltered in the tents, said Khalil Abdulrahman, a Syrian activist working with the refugees.

“It’s really cold. People don’t want to stay here. They just want to go to Turkey,” he said. If Turkey opened its border, the entire population of the province would probably flee, “and then the whole area will be empty.”

Syrian refugee Hatice Henidil hugs her grandson, Usame, while waiting Wednesday for the boy’s parents near the town of Kilis, in south-central Turkey. The parents were still on the Syrian side of the border. (Bulent Kilic/AFP/Getty Images)

That is a major concern for Turkey. Allowing the refugees into Turkey would serve only to facilitate the Russian-backed effort to drive out the rebels and also the local, mostly Sunni population of northern Syria, which turned against Assad’s regime five years ago, top Turkish officials said.

“With every refugee that we accept, in a way, we would be contributing to this ethnic cleansing aim,” Turkish Prime Minister Ahmet Davutoglu told reporters during a visit to The Hague. “If this is a strategy to change the demography in Syria, then we all have to be vigilant against it.”

In the Turkish capital of Ankara, President Recep Tayyip Erdogan called what was happening in northern Syria “a deportation” and “genocide.” He accused the international community of double standards in asking Turkey to admit refugees while most other countries in the world refuse to do so.

“We have taken 3 million Syrians and Iraqis into our home. How many did you take? Which country took them in? Are you mocking us?” he asked, pointing out that Turkey has spent $10 billion on housing refugees in recent years while the United Nations has contributed $455 million.

“Those who regard refugees as bogeymen have turned a blind eye, a deaf ear to the Assad regime, which is the reason for this problem,” he added.

The comments followed an appeal by the U.N. High Commissioner for Refugees on Tuesday to admit “all civilians who are fleeing danger and seeking international protection,” in accordance with international laws.

The New York-based advocacy group Human Rights Watch joined the appeals for Turkey to admit the refugees. “Forcing people to remain in a war zone, where they risk death and injury, is no solution to the challenge of protecting Syrians fleeing their country,” it said in a statement.

A victory for government forces­ in the Aleppo area would also put hostile forces­ up against the border of Turkey, which has been the region’s most vocal and active supporter of the rebellion to topple Assad. The loyalist force advancing on Aleppo is made up of government troops but also sizable numbers of allied Shiite militias from Iraq and Lebanon, as well as Iranian advisers with the Revolutionary Guard Corps.

Kurdish forces with the People’s Protection Units, or YPG, are also advancing in the area, another nightmare for Turkey at a time when it is waging its own war against separatist Kurds in southeastern Turkey.

The Kurdish dimension has further complicated U.S.-led efforts to forge a united front in the fight against the Islamic State and a peace settlement in Syria.

The United States’ growing friendship with the YPG is at the heart of a brewing dispute with Turkey that is jeopardizing cooperation between the allies in the war against the Islamic State. Turkey regards the YPG as a terrorist organization, but the United States, which has provided arms and air cover to the Kurdish militia to battle the Islamic State, does not.

Erdogan on Wednesday challenged the Obama administration to choose which ally to support. “Are you on our side or the side of the terrorist organizations?” he asked.

Zakaria Zakaria contributed to this report.

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Today's coverage from Post correspondents around the world