Syria conflict: US may leave F-16s and missiles in Jordan
The US says it will send a Patriot missile battery and F-16 fighters to Jordan for military exercises and might keep them there to help deal with the threat from the conflict in Syria.
A US official said the arms may be kept there in light of "escalating violence along Jordan's borders".
Secretary of State John Kerry said Syria was at risk of "total implosion".
Meanwhile, the UN is due to publish its latest report into human rights violations in Syria.
The report, the fifth of its kind, is widely expected to contain more evidence of atrocities amounting to war crimes and crimes against humanity.
It comes amid diplomatic efforts, led by the US and Russia, to organise peace talks later this month. So far diplomats have been unable to set a date for the meeting.
US Department of State spokeswoman Jen Psaki said no decision had yet been made over whether to keep the missile launcher and F-16s in Jordan.
"Given our strong alliance with Jordan and in light of circumstances in the region and escalating violence along Jordan's borders, if requested some [weapons] may remain beyond the conclusion of the exercise to assist the Jordanian armed forces," she said.
It was not clear how many F-16s would be sent. Nato already positioned Patriot missile batteries near Turkey's border with Syria earlier this year.
The batteries are designed to intercept Scud missiles, but could also potentially be employed to enforce a no-fly zone.
US President Barack Obama's administration has been coming under pressure at home and abroad to take more forceful action over Syria.
Speaking of the attempt to organise a peace conference, Mr Kerry said: "This is a very difficult process, which we come to late.
"We are trying to prevent the sectarian violence from dragging Syria down into a complete and total implosion where it has broken up into enclaves and the institutions of the state have been destroyed," he said.
The conference aims to bring representatives of the government and rebel groups together to negotiate over a plan published last year that provides for a ceasefire and a transitional government.
Mr Kerry said the conference was dependent on "events on the ground and the participants themselves".
"The Unites States can push and cajole... but in the end, the people on the ground, are going to have to decide that that's something they are prepared to engage in," he said.
At least 80,000 people have been killed and 1.5 million have fled Syria since the uprising against President Bashar al-Assad's government began in 2011.