TEHRAN: A British Parliament delegation arrived in Tehran on Tuesday on the first visit by UK lawmakers to Iran in years, as the two countries work to improve relations and ahead of continued talks on the country's disputed nuclear program.

The four-member delegation was headed by former Foreign Secretary Jack Straw, who last visited Iran in 2003 as Britain's top diplomat, Iran's official news agency IRNA reported.

Semi-official ISNA news agency reported that Straw told his Iranian counterparts he is ''optimistic'' that a November deal between Iran and world powers over the nuclear program will be realized. He also met Iran's Foreign Minister Mohammad Javad Zarif.

Last November, Iran agreed to cap its nuclear enrichment program in return to easing some sanctions by the West. Both sides have held three rounds of expert-level talks about how to implement the interim deal.

European Union and Iranian officials will meet again this week to try to finalize details on the implementation.

EU negotiator Helga Schmid will hold talks in Geneva with Iran's deputy foreign minister Abbasa Araghchi, an EU spokeswoman said Tuesday in Brussels.

Negotiators last met Dec. 30. ''Progress was made, but some issues remain to be resolved,'' said EU spokeswoman Maja Kocijancic.

''Contacts continue in order to finalize a common understanding of the implementation arrangement. The Schmid-Araghchi meeting in Geneva is part of these contacts.''

In Tehran, Foreign Ministry Spokeswoman Marzieh Afkham said: ''We hope that a couple of remaining issues, not yet agreed upon during the expert level nuclear talks, could be finally resolved during the talks.

''Separately, visiting German lawmaker Andreas Schockenhoff, a member of Chancellor Angela Merkel's Christian Democrat party, also met Iranian counterparts in Tehran.

It is the fourth time groups of European parliamentarians have visited since Iran's new president, moderate Hassan Rouhani, took office in August. Rouhani has vowed a softer approach toward the West.

The British Embassy in Tehran was closed in late 2011 after hardliners overran the building. Iran's embassy was also closed in London but relations have improved in recent months.

Both Britain and Germany and other members of the UN Security Council are at odds with Iran, and suspect the country seeks a nuclear bomb.

Tehran denies charges it is seeking nuclear weapon, insisting its nuclear program is for peaceful purposes only.