United Nations Secretary-General Ban Ki-moon says there doesn't seem to be any prospect for peace any time soon in the Syrian conflict.
At his year-end news conference, Ban said there was no sign of dialogue between the government and rebel fighters aimed at ending the 21-month-old conflict.
The UN chief also condemned the killings of polio-vaccine workers in Pakistan
, calling them "cruel, senseless, and inexcusable acts."
Eight people involved in the antipolio campaign were killed over two days. Islamic militants have claimed responsibility.
Ban also said the Middle East peace process was in a "deep freeze."
He again expressed concern about Israeli settlement-building plans, saying more Israeli construction in disputed areas "gravely" threatened efforts to establish a viable Palestinian state.
Syria: 'Potential For Sectarian Atrocities'
On Syria, the UN chief said he was "deeply concerned" about what he described as "the increased militarization of the conflict and the potential for sectarian atrocities."
"Syria began the year in conflict and ends the year in war. Day by day the death toll has climbed. Month by month the regional spillover has grown," Ban said.
"The Syrian opposition is coming together. This is critical."
Ban took a hard line against the attacks on the polio-eradication campaign in Pakistan. He said the country's children were being denied life-saving health services by those who launched the murder campaign against vaccination workers.
Pakistan is one of only three countries in the world -- the other two are Afghanistan and Nigeria -- where polio is still considered a major threat.
"Those killed were among thousands across Pakistan, especially women, who are working selflessly to achieve the historic goal of polio eradication," Ban said.
Mideast Peace Talks In 'Deep Freeze'
Ban said it appeared to him that the Israelis and Palestinians are "more polarized" than at any time since the 1993 Oslo Accords that launched the peace process. He described the peace process as being in a "deep freeze."
"The two sides seem more polarized than ever and the two-state solution is further away than at any time since the Oslo process began," Ban said.
Peace talks between Israel and the Palestinians have been stalled for the past two years, with the Palestinians demanding that Israel halt all settlement expansion before further negotiations.
Ban repeated his view that Israel's planned construction of thousands of new housing units on land the Palestinians want for a future state marks a serious threat to a two-state solution.
"I'm deeply concerned by heightened settlement activity in the West Bank, in particular around Jerusalem. This gravely threatens efforts to establish a viable Palestinian state," he said.
"I call on Israel to refrain from continuing on this dangerous path."
Ban's statement came the same day that the entire UN Security Council -- except for Israel's ally the United States -- released new statements condemning Israel's building plan.
The United States opposes Security Council involvement in the question, but earlier this week offered a separate statement critical of Israel's construction announcements.
With reporting by AP, AFP, dpa, and Reuters