United States President Donald Trump will meet Qatar's prime minister at the White House on Monday, as diplomatic efforts to end the conflict with Iran face serious obstacles.

The meeting with Sheikh Mohammed bin Abdulrahman Al-Thani, who also serves as Qatar's foreign minister, will be held behind closed doors, according to the White House schedule. Vice President JD Vance is also due to meet the Qatari leader, a US official said.

Qatar has played a central role as an intermediary between Washington and Tehran, passing on proposals and trying to bridge differences over Iran's nuclear programme and the terms for ending a conflict that has dragged on for months.

The talks come at a difficult moment. Secretary of State Marco Rubio said on Sunday that negotiations with Iran had made little progress and that he did not see an imminent breakthrough. Speaking before leaving Florida for a meeting of G7 foreign ministers in Paris, Rubio said Mr Trump preferred a diplomatic solution, but described Iran's demands as unacceptable and, in some cases, outrageous and ridiculous, and really not realistic.

Mr Trump struck a similar balance on Sunday. He said he was highly unlikely to order new strikes against Iran if negotiations made progress and produced a strong agreement. At the same time, he warned that the United States had identified additional infrastructure targets, including bridges, should military action resume.

The warning underlined how close the region remains to renewed fighting even as diplomacy continues. The United States has kept three aircraft carriers in the region, and both sides have traded threats in recent days over what would follow if talks collapse.

Qatar's mediation role has grown steadily through the crisis. The Gulf state has hosted indirect contacts between the two sides and carried messages in both directions, a position that reflects its longstanding ties with Washington and its channels to Tehran.

For the White House, the meeting is a chance to test whether Doha can unlock movement that direct exchanges have so far failed to produce. For Qatar, it is another step in a mediation effort that has become one of the most closely watched diplomatic tracks in the region.

No details of the agenda have been released beyond the Iran talks, and neither side has said whether any announcement is expected after the meeting. With Mr Rubio publicly downplaying the chances of a quick breakthrough, expectations in Washington appear modest.

What happens next is likely to depend on whether the proposals Qatar is carrying can narrow the gap between the two sides. Until then, the diplomacy continues against the backdrop of a military build-up that neither side has shown any sign of easing.