The foreign secretary, William Hague, admitted last week there was not much more Britain could do to halt the Syrian crackdown, while his US counterpart, Hillary Clinton, has been reduced to counting the dead.

But Turkey, Syria's more powerful neighbour, is less supine. It is sending its foreign minister to Damascus on Tuesday to read the riot act to Syria's gore-soaked president, Bashar al-Assad.

Ahmet Davutoglu's visit comes against a backdrop of daily atrocities by a regime struggling to contain the uprising. At least 42 civilians died on Sunday in army attacks on the eastern town of Deir Ezzor, activists said. Ten deaths were also reported in Houleh in central Syria. Belated promises from the regime of free, multiparty elections appear to have done nothing to defuse the crisis, which has claimed 1,600 lives since March.

Turkish alarm, bordering on anger, is humanitarian and strategic in nature. A summer cross-border surge of Syrian refugees has caused big headaches for Ankara. Recep Tayyip Erdogan, Turkey's prime minister, pictured right, is said to be furious that his personal pleas to Assad to stop butchering his people and adopt substantive reforms have been ignored. Erdogan has publicly condemned the regime's "savagery".

But Turkey is also worried by the impact of the unrest on its efforts to suppress Kurdistan Workers' party (PKK) fighters active in the south-east of the country, many of whom are Syrian-born or based in Syria. A report by the National Intelligence Organisation (NIT), obtained by Today's Zaman newspaper, says about 1,500 PKK fighters in the Kandil mountains region, straddling Turkey, Iraq, Syria and Iran, are of Syrian origin.

The report's complaint that Syria is not co-operating adequately with Turkish anti-terrorism efforts recalls the 1990s, when Syria provided safe haven for the PKK, hosted its now jailed leader, Abdullah Ocalan, and the two countries almost went to war amid other disputes about water resources and territory. Relations have since improved but those gains are rapidly dissipating.

Iran's refusal to share intelligence about its own anti-Kurd operations and its tightening links with the Syrian regime are another cause of Turkish concern. Davutoglu confirmed on Friday that an Iranian arms shipment to Syria had been intercepted, supposedly destined for Hezbollah in Lebanon. A Syria-bound planeload of Iranian automatic rifles, rocket launchers and mortars was seized in March.

As Assad has grown more isolated, his alliance with Tehran has gained greater importance – and become more worrying for Turkey, whose attempts to act as a go-between with Iran and western countries, for example on the nuclear issue, have irritated both sides and achieved no appreciable progress.

Against this backdrop, Davutoglu's Damascus visit has taken on the appearance of a showdown. "We have been very patient until now, waiting to see … whether they will listen to what we have been saying … But our patience is running out now," Erdogan said at the weekend.

What happens in Syria was an "internal affair" for Turkey, he said, given shared historical and cultural ties, and an 850km (530-mile) common border. "We cannot remain a bystander."

Speculation is rife that if rebuffed again, Turkey may consider punitive steps ranging from diplomatic and economic measures targeting the regime to the setting up of some kind of safe haven inside northern Syria policed by the Turkish military. If such a risky intervention were undertaken, Turkey would be within its rights, following the Libyan model, to call on fellow Nato members, including Britain, for support.

Turkey's determination to beard Assad in his lair comes amid growing Arab criticism of Syria, reflected in the Gulf Co-operation Council's weekend call for an end to the use of "excessive force" and the pursuit of "serious reform". Last week, Russia, a traditionally protective ally, backed a condemnatory UN security council statement. President Dmitry Medvedev warned Assad he would meet a "sad fate" if he did not change course.

All of which suggests Hague's appeal to regional and non-western governments to do more to pressure Assad has been heard. It highlights a probable, recurring 21st-century theme. Where Britain and the US increasingly cannot or will not act, others take the lead – and may do better.