US President Donald Trump signed two executive orders on Thursday in a new but narrower attempt to curtail birthright citizenship, once again challenging a provision of the US Constitution even though the Supreme Court rejected his previous effort.

Limiting birthright citizenship has been one of the top priorities in the Republican president's crackdown on immigration, with the White House taking particular aim at what it calls "birth tourism," in which pregnant foreigners travel to the US to give birth.

After his June 30 setback in the Supreme Court, Trump called on Congress to act, but on Thursday he opted for executive orders, which set policy but do not carry the same weight as laws passed by Congress.

The Supreme Court had struck down as unconstitutional Trump's earlier executive order, which targeted a wide swath of immigrants in the country illegally or temporarily.