A federal judge in the US has temporarily blocked an order by Donald Trump targeting some asylum seekers arriving at the country's southern border.

In a presidential proclamation issued earlier this month, the Trump administration issued an order saying immigrants "will be ineligible to be granted asylum" if they did not file their request at a legal border checkpoint.

It came as a caravan of thousands of Central American migrants made their way through Mexico towards the US border - a situation that the US President has frequently commented on in recent weeks.

The US President claimed he was issuing the proclamation to "protect the national interest, and to maintain the effectiveness of the asylum system for legitimate asylum seekers who demonstrate that they have fled persecution and warrant the many special benefits associated with asylum."

However, the move prompted swift legal action from various civil rights groups such as American Civil Liberties Union - who claimed the proclamation violated immigration law and effectively amounted to an 'asylum ban'.

While a court decision has yet to be reached, a San Francisco court has now granted a temporary restraining order blocking Trump's move until a final decision is reached in court.

In a court order, Judge Jon S Tigar writes: "Whatever the scope of the President’s authority, he may not rewrite the immigration laws to impose a condition that Congress has expressly forbidden."

He adds: "Plaintiffs and the immigrants they represent will suffer irreparable injury if the rule goes into effect pending resolution of this case. Asylum seekers will be put at increased risk of violence and other harms at the border, and many will be deprived of meritorious asylum claims.

"The government offers nothing in support of the new rule that outweighs the need to avoid these harms."

It comes amid reports in the US that the thousands of troops deployed to the border by the Trump administration to meet the caravan will soon start withdrawing.

Army Lt Gen Jeffrey Buchanan told Politico the troops 'should be home by Christmas'.

Critics had claimed the Trump administration's decision to deploy 5,800 troops to the border was a 'stunt' ahead of the recent mid-term elections.