Jordan on Tuesday rejected Syrian accusations that "terrorists" were being given military training on its soil, insisting Amman favored a political solution to its neighbor's conflict.
The Syrian foreign ministry, in a protest letter sent to the United Nations on Monday, alleged Jordan "provides logistical support to armed terrorist groups, including (Al Qaeda affiliate) Al-Nusra Front".
It accused Jordan of having "set up terrorist training camps on its soil as well as operation centers to help these groups and facilitate the infiltration of thousands of terrorists a day."
Syria's government refers to all those seeking President Bashar al-Assad's ouster as "terrorists".
Jordan's government spokesman Mohamed al-Momani, quoted by state news agency Petra, said the charges had "no basis in reality".
"Jordan does not accept that its … support for the Syrian people and for a political solution be put in doubt.
"It is in Jordan's interest for Syria to be safe, stable and capable of containing its problems within its own borders," said Momani, stressing his country was hosting almost 1.5 million Syrian refugees at a cost of $2.9 billion a year.
Syria's letter urged the UN Security Council to take measures "to stop the actions of Jordan that threaten security and stability in the region and the entire world".
Last month, rebel groups including Islamists seized the key Nasib border crossing between Syria and Jordan, the last post between the countries that remained under regime control.
Jordan is a leading supporter of the Syrian opposition, and this month the United States began training opposition fighters on Jordanian soil to fight the Islamic State (ISIS) jihadist group.
Momani himself said earlier this month: "The war against terrorism is our war and the war of Arabs and Muslims to protect our interests and the security and safety of our peoples."
Jordan announced in March that it would help train Syrian tribesmen to take on ISIS.