The latest round of indirect talks between the United States and Iran over Tehran's nuclear program has ended without a concrete agreement, as the threat of war in the Middle East mounts. The two sides emerged from hours of talks in Geneva on Thursday, with no clear sign of easing tensions.

Omani Foreign Minister Badr al-Busaidi, who is mediating the talks, said there had been “significant progress,” but no concrete agreement was made. Before the talks ended, Iranian state television said Tehran was committed to continuing uranium enrichment, rejected offers to ship enriched material abroad and reiterated its stance that international sanctions should be lifted.

US President Donald Trump wants an agreement to completely halt Iran’s nuclear program. He sees an opportunity to increase pressure as Iran is weakened by internal discontent. But Iran has refused to discuss its long-range missile program or support for groups such as Hamas and Hezbollah, saying it has the right to enrich uranium for peaceful purposes.

Technical-level talks will continue next week at the headquarters of the International Atomic Energy Agency (IAEA) in Vienna, al-Busaidi said. The IAEA’s role is expected to be crucial in any possible agreement.

Iranian Foreign Minister Abbas Araghchi described the talks with the US side as the “most intensive and longest phase of negotiations.” He warned in an interview with India Today that a possible war would be “devastating” and that a US attack could spread throughout the region. Iran has warned that it could target US military bases and even Israel.

International Crisis Group analyst Ali Weiz said the US team’s decision not to leave immediately after the talks was a positive sign. According to him, there appears to be some common ground between the two sides.

The talks, which were suspended after Israel launched a 12-day war against Iran last year and the US attacked Iran’s nuclear sites, resumed this time.

The talks, which lasted about three hours, were resumed after a short break. Iranian Foreign Ministry spokesman Esmail Baghai said that “constructive proposals” were put forward on the nuclear issue and sanctions relief.

US Secretary of State Marco Rubio has accused Iran of trying to rebuild elements of its nuclear program. Iran has not allowed IAEA inspectors into the bombed sites, despite claiming it has not been enriching since June. Satellite images have been released showing activity in those areas.

After the US withdrew from the 2015 nuclear deal, Iran increased its uranium enrichment to 60 percent, which is considered close to 90 percent weapons-grade. According to US intelligence assessments, Iran appears to be strengthening the necessary infrastructure even if it has not formally restarted its weapons program.

If the talks fail completely, the size and purpose of a possible military action are unclear. It remains unclear whether a limited attack will subdue Iran or push it towards a long-term war. Such a move is expected to spread tensions to the Persian Gulf and Israel.